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COMMENTS  ON  THE  EXPERIMENTS 
OF  NILSSON  AND  BURBANK 


HUGO  DE  VRIES 

PROFESSOR   OV   BOTANY   IN   THE  UNIVERSITY  OF   AMSTERDAM 


M 


CHICAGO 
THE  OPEN  COURT  PUBLISHING  CO. 

London:  Kegan  Paul,  Trench,  Trubner  &  Co.,  Ltd. 
1907 


Copyright  by 
THE  OPEN  COURT  PUBLISHING  CO. 

1907 


PREFACE 

Under  the  influence  of  the  work  of  Nilsson,  Burbank, 
and  others,  the  principle  of  selection  has,  of  late,  changed 
its  meaning  in  practice  in  the  same  sense  in  which  it  is  chang- 
ing its  significance  in  science  by  the  adoption  of  the  theory 
of  an  origin  of  species  by  means  of  sudden  mutations.  The 
method  of  slow  improvement  of  agricultural  varieties  by  re- 
peated selection  is  losing  its  reliabiUty  and  is  being  supplant- 
ed by  the  discovery  of  the  high  practical  value  of  the  ele- 
mentary species,  which  may  be  isolated  by  a  single  choice. 
The  appreciation  of  this  principle  will,  no  doubt,  soon  change 
the  whole  aspect  of  agricultural  plant  breeding. 

Hybridization  is  the  scientific  and  arbitrary  combination 
of  definite  characters.  It  does  not  produce  new  unit-char- 
acters; it  is  only  the  combination  of  such  that  are  new. 
From  this  point  of  view  the  results  of  Burbank  and  others 
wholly  agree  with  the  theory  of  mutation,  which  is  found- 
ed on  the  principle  of  the  unit-characters. 

This  far-reaching  agreement  between  science  and  prac- 
tice is  to  become  a  basis  for  the  further  development  of 
practical  breeding  as  well  as  of  the  doctrine  of  evolution. 
To  give  proof  of  this  assertion  is  the  main  aim  of  these  Essays. 

Some  of  them  have  been  made  use  of  in  the  delivering  of 
lectures  at  the  universities  of  California  and  of  Chicago 
during  the  summer  of  igo6  and  of  addresses  before  various 
audiences  during  my  visit  to  the  United  States  on  that  oc- 
casion.    In  one  of  them   (II.  D.),  the  main  contents  have 


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vi  PREFACE 

been  incorporated  of  a  paper  read  before  the  American 
Philosophical  Society  at  their  meeting  in  honor  of  the  bi- 
centennary  of  the  birth  of  their  founder,  Benjamin  Franklin, 
April,  1906. 

The  results  of  Xilsson  have  been  published  only  in  the 
Swedish  language;  those  of  Burbank  have  not  been  de- 
scribed by  himself.  IMy  arguments  for  the  theory  of  mu- 
tation have  been  embodied  in  a  German  book,  "  Die  Mu- 
tationstheorie"  (2  vols.  Leipsic,  Veit  &  Co.),  and  in  lectures 
given  at  the  University  of  California  in  the  summer  of  1904, 
published  under  the  title  of  "Species  and  \'arieties;  their 
Origin  by  Mutation."  A  short  review  of  them  will  be  found 
in  the  first  chapter  of  these  Essays. 


LIST   OF   ILLUSTRATIONS 


Fig.  Page. 

1.  A.  The  Oak-leaved  Hazelnut  {Corylus  Avclla)ia  laciniata), 

a  natural  sport  of  the  ordinary  hazelnut  (B)  ...  7 

2.  A.  The  toadflax  (Li)iaria  vulgaris).  B,  C.    Its  pyloric  va- 

riety.    D.    A  peloric  flower  on  an  ordinary  specimen  12 

3.  A.  The  Double-flowered    Corn-marigold  {Chrysanthemum 

segetum  plenum),  an  experimental  mutation  produced  at 
Amsterdam,  1899.  B.  A  flower-head  of  the  original  cul- 
tivated variety.  C.  The  first  result  of  selection.  D.  The 
first  sign  of  doubling.    E.  A  typical  double  flower-head  .       13 

4.  The  Experiment  Garden  in  the  botanical  garden  at  Am- 

sterdam, covered  with  iron  wire  netting.  Cultures  of 
different  Evening-primroses,  some  enclosed  in  bags  for 
artificial  pollination,  1904  ......        15 

5.  Lamarck's   Evening-primrose  {Oenothera  La'narekiana),  a 

mutating  species         .  .  .  .  .  .  .17 

6.  Leaves  of  Lamarck's  Evening- primrose  (A),  and  of  two  of 

its  mutants  (B.  Oen.  lata.     C.  Oen.  scintillans)    .  .        19 

7.  Mutants    of    the    Evening-primrose.     A.  The  red-veined 

form  (O.  rubrinervis)  which  is  of  the  same  size  as  the 
original  species.  B.  and  C.  The  dwarfish  variety  {Oen. 
nanella)   .  .  .  .  .  .  .  .  .21 

8.  A  flower-spike  of  the  giant-mutant  {Oenothera  gigas),  which 

originated  in  my  garden,  1896    .....       23 

9.  A  flower-spike  of  the  red-veined  mutant  {Oenothera  rub- 

rinervis), which  has  been  produced  almost  yearly  by  the 
parent  species  ........        25 

10.  Dr.  Hjalmar  Nilsson,  Director  of  the  Swedish  Agricultural 

Experiment  Station  at  Svalof       .....       28 

11.  Poland  wheat  {Triticum  polonicum)         .  .  .  .       2^ 

12.  A.  Bellevue  de  Talavera-wheat,  isolated  by  Le  Couteur. 

B.  Bearded  white  wheat,  produced  by  Patrick  Shirreff. 

C.  Scjuarehead  wheat,  the  most  famous  production  of 

the  same  breeder        .......       32 

13.  A.  Hallett's  pedigree  Chevalier  barley.     B.  Hallett's  pedi- 

gree wheat         .......       39 

14.  A  reproduction  of  part  of  the  first  advertisement  of  pedi- 

gree wheat  by  F.  F.  Hallett.  See  the  Times,  London, 
June  18,  Nov.  8  and  Dec.  19,  1862       ....       40 

15.  The  Swedish  Agricultural  Experiment  Station  at  Svalof. 

Part  of  the  campus  and  residence  of  the  Director  .  .       49 

16.  The  first  building  of  the  Swedish  Experiment  Station  at 

Svalof,  being  the  building  of  the  Institute  of  the  Swedish 
Seed-grain  Society     .  .  .         .         .         .         -53 


viii  PLANT-BREEDING 

Fio.  Page. 

17.  The  La])oratory  of  the  Agricultural  Experiment  Station  at 

Svalof,  Sweden  .  .  .  .  .  .  -57 

18.  The  Dairy  building  of  the  Agricultural  Experiment  Station 

S\alof,  Sweden  .......       59 

19.  Svalof  Concordia  pea,  a  most  productive  erect  new  variety 

of  green  peas,  produced  at  Svalof         ....       69 

20.  Svalof  Pearl  Summer  wheat,  not  layering,  early  rijjening, 

with  full-rounded  kernels,  that  keep  in  the  ears  at  har- 
vest time  ........        74 

21.  Ordinary  Butt  Summer  wheat,  for  comparison  with  the  im- 

proved variety  of  the  previous  figure  ....  75 
22-26.     Five  different  types  of  new  varieties  of  oats,  pjroduced 

at  Svalof.     Fig.  22.     Flag-oats            ....  76 

23.  StitT-branched  Svalof  oats       ......  82 

24.  Svalof  oats  with  spreading  branches         .  .  .  -83 

25.  Svalof  oats  with  bending  branches            ....  86 

26.  Svalof  oats  with  weak  branches       .....  87 

27.  A.  Rye  of  Schlanstedt,  produced  by  Wilhelm  Rimpjau  by 

slow  repeated  selection.     B.  Ordinary  rj-e  ...       97 

28.  Determination  of  centgener  power  of  the  progeny  of  individ- 

ual wheat  plants  at  the  Agricultural  Experiment  Station 
of  Minnesota  at  St.  Anthony  Park.  The  progeny  of  each 
parent  plant  packed  in  a  sack  for  separate  harvesting. 
The  Director,  ]Mr.  Hays  in  the  first  carriage,  August,  1904     103 

29.  Breeding  block  of  com  which  has  been  bred  for  high  oil 

content  on  the  farms  of  Funk  Bros.  Seed  Co.,  Bloom- 
ington,  111.       .  .  .  .  .  .      108 

30.  Strength  of  individual  stalks  of  corn  on  the  breeding  blocks 

of  Funk  Bros.  Seed  Co.,  Bloomington,  111.      .  .  .      109 

31.  Different  types  of  com.    A.  King  Philipp,  a  variety  of  flint 

corn.      B.  Giant  yellow  dent  corn.      C.  Rice  popcorn. 

D.  Dwarf  popcorn    .......      iii 

32.  A.  Sweet  corn,  a  cob  with  a  staminate  upper  part  and  with 

some  few  kernels  in  top.  B,  C.  Parts  of  a  tassel  of  flint 
com  bearing  staminate  spikelets  and  kernels  .  .      113 

33.  A  highly  ramified  cob  of  corn  .  .  .  .  .115 

34.  A.  A  male  or  staminate  spikelet  of  corn.     B.  A  pair  of  pis- 

tillate or  female  flowers.    After  models  of  Brendel,  Berlin     119 

35.  A.  Tassel  of  corn,  flowering  and  producing  the  anthers  from 

the  spikelets.     C.  Cob  in  the  husks,  producing  the  silks     121 

36.  Sweet  com,  with  scattered  starchy  kernels,  produced  by 

partial  cross-pollination      .  .  .  .  -123 

37.  Method  of  sacking  ear  and  tassel  in  corn  for  hybridizing. 

Agricultural  Experiment  Station,  Manhattan,  Kansas  .  125 
;^8.     The  hand  pollination  of  corn  in  one  of  the  breeding  blocks 

on  the  farms  of  Funk  Bros.  Seed  Co.,  Bloomington,  111.  126 
39.     Another    view  of  hand  pollination  in  breeding  blocks  of 

corn  of  Funk  Bros.  Seed  Co.,  Bloomington,  111.      .  ,      129 


149 


LIST   OF  ILLUSTRATIONS  ix 

Fir-  _    _  Page. 

40.  Growth  of  individual  rows  of  corn  on  the  breeding  blocks 

of  Funk  Bros.  Seed  Co.,  Bloomington,  111.    .  .  .      135 

41.  Rows  from  cobs  of  corn  which  have  been  self-fertilized  and 

from  those  which  have  not  been  self-fertilized.  The  short 
rows  being  those  self-fertilized.  On  the  breeding  blocks 
of  Funk  Bros.  Seed  Co.,  Bloomington,  111.      .  .  .      13Q 

42.  Alternate   detasseled    rows   of  corn,    at  a  later  period   of 

growth,  on  the  breeding  blocks  of  Funk  Bros.  Seed  Co., 
Bloomington,  111.        .......      1 10 

43.  View  in  the  experiment  garden  of  Amsterdam,  with  cul- 

tures of  corn  and  Evening-primroses    ....      143 

44.  Twisted  stems.     A.  Of  a  horsetail  {Equisctiim  Tchnatcja). 

B.  C)ii\\evf\\(l\.e2i?,t\  {Dipsacus  sylveslris)    .  .  .      144 

45.  Sterile  Corn,  a  special  form  of  barren  stalks  without  tassel 

and  without  ear.  Originated  in  the  botanical  garden  at 
Amsterdam,  1888       .  ......      145 

46.  Sweet    corn.     A.  With    straight    rows.    B.  With    oblique 

rows         ......... 

47  A  kernel  of  corn  cut  longitudinally.  H,  E.  Horny  endo- 
sperm. M,  E.  Mealy  or  starchy  endosperm.  S.  Scutel- 
lum.  G,  G.  Germ.  B.  The  young  bud  from  which  the 
stem  will  develop.     R.  Rootlet.    After  Frank         .  .      153 

48.  One  of  the  breeding  blocks  of  corn,  which  is  being  bred  for 

high  protein  on  the  breeding  blocks  of  Funk  Bros. 
Seed  Co.,  Bloomington,  111.     Sept.  1906        .  .  .      iSS 

49.  Luther  Burbank  of  Santa  Rosa,  Cal.        .  .  .  -158 

50.  Burbank's  farm  at  Santa  Rosa,  Cal.,  showing  the  residence, 

the  greenhouse,  the  shed,  and  part  of  the  Experiment  gar- 
den.    Photograph  of  the  S.  Pac.  R.  R.  Co.  .  .     "     .      161 

51.  Experimental  garden  of  Luther  Burbank  at  Santa  Rosa. 

A  spineless  cactus  is  seen  along  the  fence.  Cultures  of 
Echeveria  and  other  species  in  the  foreground.  Photo- 
graph of  the  S.  Pac.  R.  R.  Co.    .....     163 

52.  Luther  Burbank  in  the  garden  before  his  house  at  Santa 

Rosa,  Cal.,  receiving  a  visit  of  the  author  of  these  Essays 
(in  the  middle)  and  of  Dr.  G.  H.  Shull,  of  the  Carnegie 
Institution  (to  the  right)      ......      165 

53.  A  field  of  improved  Australian  Star-tlowers  on  Burbank's 

home  farm        ........      169 

54.  The  improved  Everlasting  Australian  Star-flower        .  •      171 

55.  A  Hybrid  Walnut  reaching  double  the  height  of  ordinary 

trees  (Juglans  Califoniica  nigra)  .  .  .  -173 

56.  Extreme  variability  in  the  size  of  seedlings  of  hybrid  wal- 

nuts in  the  second  generation       .  .  .  .  •      1 75 

57.  A  row  of  hybrid  walnuts  before  the  residence  of  Luther 

Burbank  at  Santa  Rosa.     Photograph  of  t"he  S.  Pac.  R. 

R.  Co 177 

58.  Burbank  Giant  prune    .  .  .  .  .  .  -179 


X  PLANT-BREEDING 

Fig.  Page. 

59.  Burbank  Sugar  prune    .  .  .  .  .  .  .181 

60.  The  improved  stoneless  prune.     The  pit  is  not  surrounded 

by  any  stony  material,  but  by  a  jelly    ....      190 

61.  Hybrid  Cactus  Seedlings  at  Santa  Rosa,  1904   .  .  .      191 

62.  The  Spineless  edible  Cactus,  a  hybrid  between  wild  spine- 

less species  and  the  cultivated  varieties,  growing  along 

the  fence  of  Burbank's  farm  at  Santa  Rosa  .  .  .      193 

63.  A  row  of  Shasta-daisies  ......      195 

64.  A  flower-head  of  the  fluted  variety  of  the  Shasta-daisy       .      198 

65.  The  crisp-leaved  hybrid  Heuchera  .  .  .  -197 

66.  The  crisp-leaved  hybrid  Heuchera  of  Burbank.      B,  C. 

Normal  type  of  Heuchera  leaves  ....     201 

67.  Extreme  variability  in  the  size  of  hybrid  Callas  .  .     205 

68.  A.  The  plum  and  B.  The  brown-leaved  Prunus  Pissardi, 

two  species  grafted  on  the  same  tree    .  .  .  -215 

69.  Seedlings  of  the  Spineless  edible  Cactus  in  their  first  and 

second  years.  !NIost  of  them  are  spiny,  but  the  rare 
spineless  ones  will  be  selected  for  propagation       .  .227 

70.  Seedlings  of  the  Spineless  edible  Cactus  in  their  second  year.     229 

71.  Extreme  variability  in  the  shape  of  the  leaves  of  hybrid  pop- 

pies. Second  generation  from  a  cross  l)etween  the  Bride- 
variety  of  the  opium  poppy  and  the  Oriental  poppy        .      231 

72.  A.  The  variety  the    Bride  of  the  opium  poppy.     B.  The 

wild  species  {Pa paver  pilosiim).     C.  The  hybrid  of  these 

two  poppies      .  .  .  .  .  .  -233 

73.  Flowers  of  Columbine,  showing  the  spurs         .  .  .      241 

74.  The  deadly  nightshade,  or  Atropa  Belladonna. '    A.  Brown 

flower,  and  B.  Black  fruit  of  the  species.     C.  A  twig  of 

the  yellow  variety  with  pale  flowers  and  yellow  fruits      .      243 

75.  T\\&\ox\g-\cdi\c<lWcromc2L  {Veronica  longijolia)         .  .     245 

76.  The  laciniated  bramble  {Riibiis  jruticosiis  laciniatus),   witli 

divided  petals.     B.  A  flower  of  the  ordinary  bramble     .     249 

77.  A.    Ordinary  celandine    (Clielidoniiim  ma  jits).     B.    Lac- 

iniated celandine  (C.  m.  laciniatuni),  which  originated 
from  A  in  a  garden  at  Heidelberg  about  1590.  a  and  b. 
Flowers  of  A  and  B  ......     251 

78.  Flowers  of  Evening-primroses,  deprived  of  the  petals.     A. 

The  ordinary  species  {Ocn.  biennis),  a  self-pollinating 
species  collected  near  Chicago.  B.  Summer-flower  of 
Lamarck's  Evening-primrose,  the  stigma  protruded  be- 
yond the  anthers.  C.  A  late  flower  of  the  same  plant 
with  the  anthers  touching  the  stigma   .  .  .  .252 

79.  Panicles  of  oats.     A.  With  erect  and  B.  With  spreading 

branches  ........      263 

80.  Svalof  Grenadier  wheat,  the  best  of  the  new  Swedish  varie- 

ties of  wheat,  very  productive  of  grain  and  straw  .  .      266 

81.  Svalof  Bore-wheat,  a  new  hardy  variety  for  the  cultures  of 

Middle  Sweden  .......      267 


LIST   OF   ILLUSTRATIONS  xi 

Fig.  Page. 

82.  A  panicle  of  oats,  with  weak  branches,  photographed  at 

Svalof,  Sweden  .  .  .  .  .  .  .273 

83.  A  panicle  of  oats  with   stiff  Ijranches,   photographed  at 

Svalof,  Sweden  .  .  .  275 

84.  A  spikelet  of  oat -grass  {Avena  clatior),  showing  a  flower 

with  two  palets,  three  stamens,  and  two  stigmas  (a),  a 
flowerbud  (b),  of  which  only  the  palets  are  visible, 
and  the  third  or  sterile  flower  (c)  .  .  .  .278 

85.  Barley.     A.  A  complete  spikelet  with  the  three  flowers. 

B  and  C.  Single  flowers  seen  from  different  sides,  show- 
ing two  palets,  three  stamens,  and  the  ovary  with  the 
stigmas.  In  B,  also  the  two  outer  scales  or  glumae.  D. 
Stamens  and  ovary  of  a  flower    .  .  .  .  -279 

86.  Svalof   Solo  pea,  a  new  forage-plant,  most   productive   of 

seeds  and  foliage.     Leaves  green        .          .          .  .281 

87.  Svalof  Grop  pea,  a  new  early  ripening  forage-plant   .  .      283 

88.  The  wild  oat-grass  {Avena  elatior),  a  pasture  grass    .  .     285 

89.  A  pitcher-like  leaf  of  tobacco           .          .          .          .  .291 
go.     Pitchers  of  Magnolia,  A,  B,  C.     Of  clover,    D,  E.  Of 

the     lime-tree     (Tilia),    F,     G.     One-leaved  pitchers. 

C.  Two-leaved.  A.  Upper  part  of  a  leaf  only  trans- 
formed into    a   pitcher.     D,  E.  Pitcher-like    leaflets   of 

the  ordinary  and  of  the  five-leaved  clover     .         .  .      293 

91.  A.  Seedling-plants  of  Evening-primroses.     B.  Of  the  fig- 

wort   {Scropliularia  nodosa).  C.  Of  Silene  odontipetala. 

D.  Of  poppies.  E.  Of  the  beech.  A  i  and  D  i.  Nor- 
ma,! seedlings.  A  7,  B,  C  2,  D  4,  E,  Tricotyledonous 
seedlings.  C  3,  D  5,  Seedlings  with  four  and  D  6  with 
five  seed-leaves.     A  2-6,  C  i,  D  2-3,  Different  degrees 

of  splitting  of  seed-leaves   ......      295 

92.  Polycephalous  opium  poppy.     A.  Normal  fruit.     B.  The 

same  cut  longitudinally.  C,  D.  Normal  stamens.  E,  F. 
Stamens  transformed  into  secondary  carpels.  G,  H,  I. 
Secondary'  carpels,  cut  transversely  with  one,  two,  and 
four  rows  of  seeds      .......      299 

93.  Young  plant  of  opium  poppy  in  the  sensitive  period  of  the 

development  of  the  terminal  flower,  cut  longitudinally. 
A.  Flower-head  of  ^nnn  7.  B.  Of  June  14.  C.  All  parts 
discernible.  D.  Diagram  of  flower.  E.  Diagram  of 
young  flowerbud.      P.   Petals.      S.   Stamens  .  301 

94.  The  Double  Corn-marigold,  an  experimentally  produced 

variety •      joj 

95.  \'ariability  in  the  size  of  the  ripe  fruits  of  the  Evening- 

primrose  of  Lamarck  A.  A  weak  plant  with  small 
fruits.    B.  A  tall  plant  with  large  fruits         .  .  .     305 

96.  A.  The  Pansy  and  some  of  its  parents.     B.  Viola  lutea 

grandiflora. .  C.  Viola  tricolor  versicolor.  D.  Viola  tri- 
color lutescens.     After  Wittrock  .  .  .  -311 


xii  PLANT-BREEDING 

Fig.  Page. 

97.  Gordon's  currant  {Ribes  Gordonianum),  a  hybrid  of  the 

flowering  currant  and  the  golden  currant      .  .  314 

98.  A.  The  flowering   currant    of     the    Pacific  coast     {Ribcs 

saiigniiieum).     B.  The  yeWow  currsint  (Ribes  aiireum)    .     315 

99.  A.  The   cukivated  snay:)dragon.     B-G.  Its  color  varieties. 

B.  Yellow.  C.  Delila,  tube  white  and  lips  red.  D,  E. 
Flesh-colored.  F.  Brilliant,  of  a  fiery  red.  G.  Album, 
white  with  a  yellow  spot  on  the  lip.  H.  The  calyx  and 
the  style  after  the  removal  of  the  corolla        .  .  -317 

100.     Danebrog  Opium  poppy;  petals  red  with  a  large  white  spot 

at  the  base  ........      319 

loi.  Glass-covered  part  of  the  experiment  garden  at  Amsterdam 
in  the  late  spring,  1906;  the  biennial  plants  of  the  eve- 
ing-primroses  are  flowering,  the  annual  specimens  are 
still  very  small.  Tubes  for  spraying  and  sacks  for  arti- 
ficial pollination  .  .  .  .  .  .  323 

102.  A.  The  short-styled  Evening-primrose,  and  B-F,  its  parent 

form.  b.  A  flower  after  the  removal  of  part  of  its  petals 
and  stamens,  c.  The  same  without  petals,  d.  The 
same  without  the  tube  and  calyx,  e.  A  flowerbud.  /. 
Ripe  fruits.  B-F.  The  corresponding  parts  of  the  par- 
ent species,  g.  Styles,  h.  Longitudinal  section  of 
ovar}'.  i.  Transversal  section  of  base  of  style  and  calyx- 
tube      ........  325 

103.  A  biennial  specimen  of  the  Evening-primrose  of  Lamarck   .      327 

104.  Spikes  with  almost  ripe  fruits  of     A.  Oenothera  gigas,  a 

mutant  species  and  B.  Oenothera  Lamarckiana,  its 
parent  form        ........      329 

105.  A.  A  rosette  of  root-leaves  of  Lamarck's  Evening-primrose 

in  September.  B.  A  similar  rosette  of  one  of  its  mutants 
(Oen.  scintillans)  in  the  same  age  ...  330 

106.  The  smooth-leaved  variety  of  the  Evening-primrose  {Oeno- 

thera laevifolia),  a.  A  side-flower  with  ovate  instead  of 
obcordate  petals,  one  of  the  new,  highly  varial)le  charac- 
ters of  the  new  form  ......      331 

107.  Oenothera  muricata,  a  seaside  plant  which  originated  far 

from  the  sea      ........      337 

108.  W'ulfenia  carinthiaca,  which  grows  only  on  the  Giirtnerkugel 

in  Carinthia      ........      339 

109.  The  smooth-leaved  campion,  a  local  plant  of  Hungary  with 

a  useless  character     .......      341 

no.  Two  Alpine  species  of  milfoil.  A.  The  Achillea  atrata  of 
calcareous  and  B.  The  A.  moschata  of  siliciferous 
soils _       .  -343 

111.  Palo  Verde  or  Parkin.sonia  microphylla,  a  typical  desert 

plant  from  Tucson,  Arizona         .....      346 

112.  Palo  Christi  or  Koeberlinia  speciosa,  a  typical  desert  plant 

from  Tucson,  Arizona         ......     347 


LIST    OF   ILLUSTRATIONS  xiii 

Fig.  Page. 

113.  A.  Forest  of  gir.nt  Cacti  (Ccretis  giganteiis)  near  Tucson,  in 

Arizona.     Opuntia  in   the    foreground.     Ocatillo,  tree- 
cactus  and  Palo  \'erde  in  the  middle    .... 

1 14.  The  desert  botanical  laboratory  at  Tucson,  Arizona,  with 

two  shrubs  of  Ocatillo  (Fouquieria  splnidens),  giant  cacti, 
Opuntia,  tree-cactus,  and  other  shrubs  .  .  -351 


349 


PLANT-BREEDING 

COMMENTS  ON  THE  EXPERIMENTS  OF  NILSSON  AND  BURBANK 


CONTENTS 

I.     Evolution  and  INIutation  .....         i 

II.     The  Discovery  of  the  Elementary  Species  of  Agri- 
cultural Plants  by  Hjalmar  Nilsson. 

A.  Different  Principles  in  the  Breeding  of  Cereals     .  .  29 

B.  The  Swedish  Agricultural  Experiment  Station  at  Svalof  48 

C.  The  Svalof  INIethod  of  Producing  Improved  Races         .  67 

D.  A  Criticism  of  the  Method  of  Continuous  Selection       .  90 

III.  On  Corn-Breeding     .         .         .         .         .         .         .107 

IV.  The   Production   of    Horticultural   Novelties    by 

Luther  Burbank. 

A.  :\Iethods  and  Material 159 

B.  New  Varieties  in  Fruits  and  Flowers  .  .  .178 

C.  Hybridization  and  Selection       .....      202 

D.  Mutations  in  Horticulture  .....      221 

V.     The  Association  of  Characters  in  Plant-Breeding. 

A.  Association  of  Characters  in  Nature  .  .  .237 

B.  Correlations  in  Agricultural  Breeding  .  .  .255 

C.  A  INIethodical  Study  of  Correlations  .  .  .271 

D.  Correlations  in  Fluctuating  Variability         .  .  .     289 

E.  Unit-Characters         .......     309 

VI.    The  Geographical  Distribution  of  Plants        .         .     333 
Index 353 


E^T)LUTION   AND  MUTATION 

In  the  beginning  of  the  last  century  Lamarck  founded 
the  theory  of  a  common  descent  for  all  Hving  beings.  It 
afforded  him  the  only  possible  means  of  explaining  system- 
atic affinity.  He  assumed  that  the  influence  of  the  en- 
vironment was  capable  of  changing  the  characters  of  the 
organisms,  and  of  fitting  them  for  their  Ufe  conditions.  His 
evidence,  however,  was  A'ery  scanty  and  therefore  he  failed 
in  convincing  his  contemporaries. 

Half  a  century  afterward  Darwin  brought  together  such 
an  overwhelming  mass  of  evidence  that  opposition  had  to 
give  in.  His  main  point  was  one  of  comparative  investiga- 
tion. x'Vt  his  time  it  was  universally  assumed  that  species 
had  been  created  as  such,  but  th:it  subspecies  and  varieties 
had  been  derived  from  them  according  to  natural  laws. 
Darwin  proved  that  no  such  distinction  between  species 
and  subspecies  exists.  Their  marks  are  of  the  same  nature, 
and  if  a  natural  origin  is  assumed  for  one  group,  it  must  be 
conceded  for  the  other  too.  The  same  holds  good  for  genera 
and  families,  and  even  for  the  higher  divisions  of  the  system. 

Moreover,  Darwin  showed  that  the  secjuence  of  the 
appearance  of  organisms  during  geological  times  finds  a 
natural  explanation  on  the  assumption  of  the  theory  of  de- 
scent, and  that  the  geographical  distribution  of  animals  and 
plants  is  exactly  as  we  should  expect  it  to  be  if  their  common 
origin  were  the  main  factor  in  assigning  them  their  special 
domains. 

These  broad  proofs  of  the  theory  of  evolution  are  quite 
independent  of  the  question  by  which  means  and  in  what 
way  new  species  are  produced  from  the  existing  ones.  This 
question,  however,  appeals  more  directly  to  the  imagination, 

ntOKRTY  llBRAHY 


2  PLANT-BREEDING 

and  Darwin  collected  all  the  evidence  concerning  it  which 
he  could  find.  The  rapid  victory  gained  by  his  views  has 
been  due  mainly  to  his  discussion  of  this  minor  point. 

Direct  observations  concerning  the  first  appearance  of 
species  in  nature  were  not  at  hand.  In  agriculture  and  in 
horticulture,  however,  numerous  observations  had  been  made, 
and  for  a  number  of  races  and  varieties  the  origin  was  his- 
torically known.  Distinct  methcKls  were  in  use  to  guide 
these  changes  and  to  produce  varieties  which  would  comply 
with  the  demands  of  practice.  '  The  grand  principle  of  all 
these  methods  was  selection.  Selection  means  guiding  the 
changes  in  the  specific  characters  of  organisms  by  cutting 
off  all  those  which  are  changing  in  undesirable  ways,  and 
reser\dng  for  reproduction  only  those  wliich  differ  advan- 
tageously from  the  average. 

Darwin  proved  that  the  origin  of  species  in  nature  must 
be  the  same  phenomenon  as  the  origin  of  races  and  varieties 
in  culture.  He  showed  that  in  nature  an  analogous  process 
of  selection  is  steadily  active.  More  seeds  are  produced 
and  more  children  are  born  than  can  possibly  survive,  and 
the  decision  as  to  which  are  to  live  and  wliich  must  die  dc- 
y)ends,  on  one  side,  on  the  life  conditions  and,  on  the  other, 
on  the  distinctive  qualities  of  the  competing  indi\iduals.  Of 
course,  in  the  single  instances  survival  depends  mainly  on 
chance,  but  in  the  long  run  the  cUfferent  chances  may  be 
assumed  to  annul  one  another's  influence,  and  the  decision 
falls  to  indi\ddual  excellences  and  life  conditions.  In  this 
way  the  latter  can  be  said  to  make  a  choice  of  the  individuals 
best  fitted  for  the  local  conditions  and  this  is  what  is  now 
universally  known  as  iJie  principle  oj  natural  selection. 
It  guides  evolution,  keeping  it  in  the  useful  ways,  and  des- 
troys all  that  try  to  diverge  in  opposite  directions. 

The  theory  of  common  descent  is  Darwin's  theory,  since 
it  has  been  founded  by  him  on  so  broad  a  basis  of  facts  as  to 


EVOLUTION   AND    3.IUTATION  3 

insure  almost  universal  acceptance.  The  theory  of  natural 
selection  is  one  of  the  means  by  wliich  this  position  has  been 
reached.  It  is  the  appKcation  of  the  breeding  practice  to 
the  phenomena  of  nature  at  large.  Darwin's  theory  is 
often  designated  as  the  theory  of  natural  selection.  Tliis  is 
however,  not  the  same  as  the  theory  of  descent.  The  idea 
of  descent  with  modification,  which  now  is  the  basis  of  all 
evolutionary  science,  is  f[uite  independent  of  the  question 
as  to  how,  in  the  single  instances,  the  change  of  one  species 
into  another  has  actually  taken  place.  The  theory  of  de- 
scent remains  unshaken  even  if  our  conception  concerning 
the  mode  of  descent  should  prove  to  be  in  need  of  revision. 
Such  a  revision  has  become  necessary  by  the  gradual 
development  of  the  study  of  variabihty.  Darwin  has  demon- 
strated that  all  the  individuals  of  a  given  species  differ  from 
one  another  to  some  extent,  and  that  many  of  these  differ- 
ences increase  or  lessen  their  chances  of  survival.  A  stru2;2le 
for  life  ensues,  and,  sooner  or  later,  the  unfit  individuals 
succumb,  thereby  leaving  the  average  of  the  species  changed 
to  some  slight  degree.  Differences  between  isolated  local 
races  afford  the  means  of  studying  the  efficiency  of  this  process 
of  variability  and  selection.  The  cjuestion  arises,  however,  as 
to  how  far  this  variability  may  go  under  the  influence  of  tliis 
guidance.  Is  it  limited  or  unlimited  ?  Can  it  proceed  during 
centuries  and  in  the  same  direction,  augmenting  the  differ- 
ences to  any  extent,  or  is  it  bound  by  its  original  average 
condition,  without  l)eing  able  to  diverge  far  from  it  ?  Can 
it  produce  new  characters  and  new  qualities  or  is  it  Hmited 
to  changes  of  degree  in  those  that  already  exist?  To  all 
these,  and  many  other  questions,  an  answer  could  not  be 
given  at  the  time  of  Darwin,  the  evidence  being  too  incom- 
plete. It  was,  however,  necessary  to  make  a  decision  of 
some  kind  and  thus  it  was  universally  assumed  that  the 
changes  by  which  species  originate  are  slow,  almost  invisible, 


4  PLANT-BREEDING 

and  may  accumulate,  in  the  lapse  of  time,  to  any  degree. 
All  of  the  characters  of  living  organisms  were  simply  assumed 
to  be  due  to  this  slow  process  of  gradual  evolution  guided 
by  natural  selection. 

Here,  however,  a  first  difficulty  arose.  We  do  not  ob- 
serve actual  specific  changes  in  nature.  To  meet  tliis  ob- 
jection Darwin  assumed  the  changes  to  be  so  slow  as  to  be 
imisible  to  us.  Even  tlie  life  time  of  a  man  would  not  be 
sufficient  to  control  them.  By  this  supposition  the  evolution 
of  a  flower  or  a  seed  or  of  highly  dift'erentiated  organs  (such 
as  the  leaves  of  insectivorous  plants)  would  require  an  enor- 
mous time.  From  tliis  a  calculation  could  be  made  as  to 
the  time  required  for  the  whole  range  of  evolution  of  the 
vegetable  and  animal  kingdoms.  The  result  was  that  many 
thousands  of  millions  of  years  were  considered  to  be  the 
smallest  amount  that  would  account  for  the  development 
of  life  on  earth  from  the  very  first  beginning  until  the  appear- 
ance of  mankind. 

Phvsicists  and  astronomers  have  ol)jecte<l  to  this  con- 
clusion. The  objection  has  been  brought  forward  from  the 
time  when  Darwin  published  his  calculation.  It  has  never 
relented  and  has  often  threatened  to  impair  the  whole  theory 
of  descent.  The  results  of  physical  and  astronomical  cal- 
culations concerning  the  age  of  Ufe  on  this  earth  dilTer  so 
widely  from  the  demands  made  by  the  theory  of  slow  evolu- 
tion as  to  be  considered  incompatible  with  them.  The  de- 
ductions made  by  Lord  Kelvin  and  others,  from  the  central 
heat  of  the  earth,  from  the  rate  of  the  production  of  the  cal- 
careous deposits,  from  the  increase  of  the  amount  of  salt 
in  the  water  of  the  seas,  and  from  various  other  sources, 
indicate  an  age  for  the  inhabitable  surface  of  the  earth  of 
between  twenty  and  forty  millions  of  years  only.  This 
large  discrepancy  has  always  been  a  weapon  in  the  hands  of 
the  opponents  of  the  evolutionary  idea,  and  there  can  be  no 


EVOLUTION   AND    MUTATION  5 

doubt  that  it  proves  that  the  current  view  of  extremely  slow 
and  almost  invisible  changes  must  be  abandoned. 

Shortly  after  the  publication  of  Darwin's  Origin  of  Species, 
the  Belgian  anthropologist,  Quetelet,  submitted  the  variabil- 
ity in  measurement  of  the  different  parts  of  the  human  body 
to  a  statistical  investigation.  He  discovered  that  tliis  kind 
of  variability  follows  distinct  laws  and  that  these  laws  agree, 
in  the  main,  with  the  law  of  probability.  Small  divergences 
from  the  average  are  numerous,  larger  discrepancies  are 
rare,  and  the  rarer,  the  larger  they  are.  Variabihty  is  thereby 
limited,  and  is  subject  to  a  return  to  the  average  condition. 
It  may  be  moved  from  tliis  average,  to  some  extent,  by  a 
change  in  the  outward  conditions  or  by  a  repeated  selection 
in  one  direction ;  but,  as  soon  as  these  causes  and  this  selection 
cease  to  work,  a  return  to  the  average  is  unavoidable.  Vari- 
abihty may  augment  or  diminisli  the  ({uaHties;  it  is  linear, 
consisting  of  changes  along  a  simple  Une,  some  being  positive 
and  others  being  negative,  but  it  does  not  strike  into  new 
directions.  It  is  no  source  of  new  qualities.  The  phenom- 
ena wliich  are  controlled  by  tliis  law  and  which  are  bound 
to  such  narrow  limits  cannot  be  a  basis  for  the  explanation 
of  the  origin  of  species.  It  governs  quantities  and  degrees 
of  quahties,  but  not  the  qualities  themselves.  Species, 
however,  are  not,  in  the  main,  distinguished  from  their 
allies  by  quantities  or  by  degrees  —  their  very  qualities  may 
differ. 

From  this  cUscussion  it  may  be  seen  that  the  slow  and 
gradual  changes  of  ordinary  variability  and  the  production 
of  new  characters  are  not  of  the  same  order.  Variabilitv, 
in  the  ordinary  sense  of  the  word,  is  a  broad  conception. 
It  must  be  subdivided  for  the  purpose  of  scientific  investiga- 
tion. The  phenomena  that  follow  Quetelet's  law  are  now 
considered  as  one  group,  which  is  called  fluctuating  variabilitv 
or  fluctuation,  since  the  individual  qualities  fluctuate  around 


6  PLANT-BREEDING 

their  average.  The  processes  by  which  new  quahties  are 
produced  must  be  studied  separately.  Under  the  assump- 
tion that  these  processes  are  neither  slow  nor  invisible,  but 
consist  in  leaps  and  jumps  such  as  are  popularly  indicated 
by  the  name  of  sports,  they  are  now  called  mutations,  and 
this  great  subdivision  of  the  phenomena  of  variability  is 
designated,  in  consequence  thereof,  as  mutability. 

Darwin  was  well  aware  of  the  existence  of  different  cases 
of  variabiUty,  and  of  the  possibility  of  their  bearing  on  the 
theory  of  evolution.  He  consid:,':c  the  assumption  of  an 
origin  of  species  in  nature  by  leaps  and  sports,  such  as  were 
observed  to  occur  among  horticultural  plants.  He  pointed 
out  that  the  affinity  of  closely  allied  species  can  be  explained 
on  this  assumption  as  well  as  by  slow  changes.  If  we  con- 
sider all  the  varieties  and  subspecies  of  apples,  or  beets,  or 
of  one  of  the  cereals,  and  assume  thousands  of  years  for 
their  production,  the  changes  may  have  been  brought  about 
by  rare  sports  as  well  as  by  long  continued  changes;  the 
effect,  at  the  present  time,  would  be  the  same.  Darwin 
agreed  that  this  possibility  could  not  be  denied  and  that  it 
was  a  very  weak  point  in  his  hypothesis  of  slow  evolution. 

The  mutations  must  not  be  assumed  to  be  considerable 
changes.  From  a  study  of  the  differences  among  small 
species,  we  may  form  some  conclusion  as  to  their  probable 
size.  Common  observation  shows  the  difference  between 
clHed  species,  ordinarily,  to  be  quite  striking;  but  a  little 
discussion  and  a  closer  inspection  will  easily  prove  that,  in 
such  cases,  the  differences  are  due  to  more  than  one,  and 
often  to  numerous,  characters.  In  groups  (such  as  bram- 
bles, roses,  buttercups,  willows,  and  many  others),  where 
large  numbers  of  species  are  closely  allied,  the  differences 
between  any  two  of  them  become  smaller,  and,  the  number 
of  cUstinct  forms  increasing,  the  distinction,  in  the  end,  may 
become  reduced  to  one  single  differential  mark  for  each  two 


Fig.  I      A.  The  Oak-leaved  Hazelnut  (Cor>'/H5. 4 tr//<7»a/acm/a/a),  a  natural 
sport  of  the  ordinary  hazelnut  (B). 


8  PLANT-BREEDING 

neighboring  types.  Such  differences  must  be  assumed  to 
be  produced  each  by  a  single  mutation.  By  tliis  means 
the  significance  of  the  mutations  may  best  be  judged,  and 
whenever  species  dift'er  from  their  nearest  alUes  in  a  higher 
degree,  the  inference  is  allowed  that  they  have  been  origin- 
ated by  more  than  one  mutation. 

Since  the  pubhcation  of  Darwin's  theory,  the  probabil- 
ity of  such  sudden  changes  playing  an  important  part  in  the 
evolution  of  species  has  always  found  some  support.  Of  late, 
the  evidence  has  increased  in  this  direction,  especially  under 
the  influence  of  Cope.  Discontinuous  evolution  has  been 
defended  among  pakeontologists  by  Dollo,  among  zoolo- 
gists by  Bateson,  and  among  botanists  by  Korshinsky.  This 
Russian  author  compiled  the  history  of  a  large  number  of 
varieties  from  the  widely  scattered  horticultural  literature 
and  showed  that,  in  almost  all  cases  where  the  history  of 
the  origin  of  a  variety  was  recorded,  it  originated  suddenly. 
Alany  other  varieties,  especially  among  trees  and  shrubs, 
have  been  discovered,  as  such  in  the  field,  and,  although 
their  origin  is  not  historically  known,  the  constant  absence 
of  intermechates  pleads  vigorously  for  the  explanation  of 
their  differential  rjuahties  by  mutation. 

The  conception  of  mutations  agrees  with  the  old  view 
of  the  constancy  of  species.  Tliis  theory  assumes  that  a 
species  has  its  birth,  its  lifetime,  and  its  death,  even  as  an 
individual,  and  that  throughout  its  life  it  remains  one  and 
the  same.  Thus  it  is  only  natural  that  wild  species  are 
almost  always  observed  to  be  constant,  since  by  a  mutation 
they  do  not  change  themselves  but  simply  produce  a  new 
type.  This  is  allied  to  its  ancestor  as  a  branch  is  to  a  tree, 
the  stem  continuing  its  own  growth,  no  matter  how  many 
branches  it  produces.  Just  so  a  species  may  produce  quite 
a  number  of  new  forms  without  being  changed  itself,  in  the 
the  least,  thereby.     Among  palasontologists  Scott  has  gi^'en 


EVOLUTION   AND   MUTATION  9 

forth  this  same  view.  According  to  his  conception,  species 
are  derived  from  one  another  by  small  shocks.  Each 
shock  caused  the  old  hmits  to  be  transgressed;  but,  after 
it,  the  new  species  remained  unchanged  until,  perhaps  after 
centuries,  a  new  shock  made  it  transgress  its  new  Hmits. 
Each  single  type  (be  it  species,  subspecies,  or  variety)  is 
thus  wholly  constant  from  its  first  appearance  and  until  the 
time  it  disappears,  either  after,  or  without,  the  production 
of  daughter  species. 

On  the  ground  of  the  mutation  theory,  there  is  a  struggle 
for  life  among  species  as  well  as  among  individuals.  There 
is  selection,  also,  between  competing  species  and  among 
the  incUviduals  of  the  same  species;  the  fittest  will  survive, — 
but  tliis  holds  good  for  species  as  well  as  for  individuals. 
As  to  individuals,  natural  selection  may,  to  some  extent, 
cause  a  divergence  from  the  average  type.  But  among 
species,  natural  selection  is  the  most  potent  factor,  since  it 
eliminates  some  and  therel)y  protects  and  favors  others. 
Thus  we  come  to  the  conclusion  that  natural  selection  is 
as  active  as  Darwin  assumed  it  to  be,  and  is  as  pre-eminent 
a  factor  in  the  process  of  evolution.  It  causes  the  survival 
of  the  fittest;  but  it  is  not  the  survival  of  the  fittest  individ- 
uals, but  that  of  the  fittest  species,  by  wliich  it  guides  the 
development  of  the  animal  and  vegetable  kingdoms. 

Resuming  the  main  point  of  this  discussion,  we  may 
sketch  the  origin  of  species,  according  to  the  theory  of  mu- 
tation, in  the  following  manner.  Species  are  derived  from 
other  species  by  means  of  sudden  small  changes  which,  in 
some  instances,  may  be  scarcely  perceptible  to  the  inexper- 
ienced eye.  From  their  first  appearance  they  are  uniform 
and  constant,  when  propagated  by  seed;  they  are  not  con- 
nected with  the  parent  species  by  intermediates  and  have 
no  period  of  slow  development  before  they  reach  the  full 
display  of  their  characters.     They  do  not  always  arise,  but 


lo  PLANT-BREEDING 

only  from  time  to  time.  A  parent  species  may  produce  its 
offspring  separately  at  intervals,  or  in  larger  numbers  during 
distinct  mutating  periods.  After  this  production,  the  old 
species  is  still  the  same  as  it  was  before,  and  it  subsists  in 
the  midst  of  its  children.  New  forms  are  produced  by  the 
old,  either  in  one,  or  a  few,  or  in  numerous  incUviduals;  in 
the  latter  case,  the  chance  of  survival  is  evidently  enhanced. 
Some  young  species  will  be  better  fitted  for  their  life- 
conditions  than  others,  and  the  struggle  for  life  will  induce 
a  selection  among  them  by  which  the  fittest  survive.  Even 
as  the  new  species  are  produced  locally  and  as  the  effect 
of  local  causes,  the  struggle  for  life  and  natural  selection 
decide  concerning  the  survival  according  to  the  local  con- 
ditions. These  conditions  thus  have  a  twofold  significance 
for  the  development  of  the  pedigree  of  the  main  groups  of 
plants  and  animals,  but  it  is  probable  that  they  determine 
the  hues  of  progress  chiefiy  by  their  selective  activity. 

The  main  arguments  in  the  discussion  of  the  production 
of  species  by  slow  changes  or  by  mutations  were  taken  by 
Darwin  from  the  experience  of  agricultural  and  horticul- 
tural breeders.  Therefore  it  is  desirable  to  inquire  into 
their  real  significance.  Do  they  support  the  one  or  the 
the  other  view?  Darwin  assumed  that  tliey  gave  proof  of 
slow  changes,  and  took  his  arguments  mainly  from  the  agri- 
cultural side.  In  horticulture,  however,  as  we  have  seen 
in  discussing  Korshinsky's  work,  the  prol)ability  is  on  the 
other  side.  In  my  experiments  on  mutabihty  I  have  shown 
that  it  is  possible  to  repeat  and  control  the  origin  of  horti- 
cultural and  analogous  varieties  under  strict  experimental 
precautions,  and  that  the  full  proof  may  be  given  that  they 
originate  at  once,  and  not  by  a  slow  process  of  changes. 
They  may,  in  the  first  instance,  appear  with  the  full  display 
of  their  average  character,  or  only  with  a  small  indication 
of  it  as  an  extreme  variant  of  its  fluctuation,  but  in  the  latter 


EVOLUTION   AND    MUTATION  ii 

case  the  average  is  often  reached  after  one  more  genera- 
tion. 

I  observed  the  origin  of  the  peloric  toadflax  and  of  a 
double  marigold,  and  produced,  almost  artiiicially,  the  twisted 
variety  of  a  Dracocephalum. 

In  the  case  of  the  toadflax,  Linaria  vulgaris  peloria,  the 
change  came  suddenly,  and  more  or  less  unsuspectedly, 
after  a  culture  of  about  eight  years.  The  ordinary  form 
produces,  from  time  to  time,  some  few  five-spurred,  regular 
or  peloric  flowers.  At  once  an  individual  arose  which  had 
such  flowers  only.  The  next  year  the  mutation  was  re- 
peated. The  seeds  of  the  mutated  individuals  reproduced 
the  new  variety  almost  exclusi^'ely,  and  each  plant  of  it  had 
peloric  flowers  only.  No  intermediates  were  observed, 
neither  in  the  number  of  the  spurs  of  the  flower  nor  in  the 
number  of  the  peloric  flowers  on  the  plants.  It  was  as  sud- 
den a  change  as  any  horticultural  sport,  but  its  ancestry 
had  been  purely  fertilized  and  carefull}  recorded  so  as  to 
leave  no  doubt  concerning  the  real  nature  of  the  mutation. 

The  double  variety  of  the  corn-marigold  (Chr^'san- 
themum  segetum)  arose  in  my  garden  in  a  culture  in  which 
I  was  increasing  the  number  of  the  ray-florets  by  contin- 
uous selection.  During  four  years  I  had  succeeded  in  in- 
creasing this  number  to  about  sixty  on  each  head,  starting 
from  the  cultivated  variety,  with  an  average  of  twenty-one. 
All  the  ray-florets,  however,  belonged  to  the  outer  rows  of 
the  heads,  as  in  the  original  variety.  At  once  a  plant  arose 
which  produced  some  few  ligulate  florets  in  the  midst  of  the 
disc.  This  indicated  the  production  of  a  double  race. 
When  the  seeds  of  this  mutating  individual  were  sown,  the 
next  year,  they  yielded  a  uniformly  double  group;  and  from 
this  time  the  new  variety  remained  constant. 

The  Dracocephalum  moldavicum  is  an  annual  garden- 
plant  belonging  to  a  genus  in  which  Morren  has  described 


^i 


Fig.  2.     A.  The  toadflax  (Lhiaria  vulgaris).     E,  C.    Its  peloric  variety.     D. 
A  jieloric  flower  on  an  ordinary  specimen. 


s;  5.'  5  hj 


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13 


14  PLANT-BREEDING 

some  beautifully  twisted  specimens.  I  succeeded  in  procur- 
ing such  a  specimen  in  this  species  by  cultivating  a  race  of  it 
during  some  few  years,  selecting  the  specimens  which 
showed  a  marked  tendency  toward  variation  in  the  arrange- 
ment of  their  leaves.  The  twisting  appeared  at  once,  but 
the  race  has  not  been   continued. 

AU  these,  and  many  other,  experiments  have  been  con- 
ducted under  conditions  which  allowed  of  a  close  scientific 
study.  They  confirm  the  common  experience  of  the  horti- 
cultural breeder  in  stating  the  suddenness  of  the  changes 
and  thv  immediate  production  of  distinct  races.  They 
show  us  the  way  in  which  analogous  changes  may  have 
occurred  in  nature,  and  make  it  probable  that  sudden  changes 
are,  at  least,  an  important  factor  in  the  evolution  of  the 
vegetable  kingdom. 

With  agricultural  crops  my  experiments  ha\'e  been  too 
rare  to  give  a  definite  result.  The  German  breeders  assumed, 
as  a  rule,  that  they  produced  their  races  at  will  and  by  a 
process  of  slow  variability  and  repeated  selection.  It  is 
mainly  upon  this  conviction  that  Darwin  has  based  his  con- 
ception of  an  analogous  slow  improvement  of  species  in 
nature.  This  (ierman  method  has,  however,  been  STib- 
mitted  to  a  severe  criticism  by  Dr.  Xilsson,  the  director  of 
the  Swedish  agricultural  experiment  station  at  Svalof. 
His  pedigree-cultures  have  shown  that  the  idea  of  a  slow 
accumulation  of  characters  by  repeated  selection  is  due  to 
incorrect  observations  and  to  the  use  of  untrustv/orthv 
methods.  According  to  his  experiments,  changes  occur  in 
agricultural  plants  as  suddenly  as  in  horticultural  species; 
there  is  no  essential  difference  between  them  in  this  respect. 
By  these  discoveries  the  main  support  of  the  theory  of  slow 
and  gradual  evolution  is  broken  down,  and  the  analogv 
between  artificial  and  natural  production  of  species  comes 
to  plead  wholly  for  the  theory  of  mutation.     These  new 


i6  PLANT-BREEDING 

facts  will  be  dealt  with  in  our  next  chapter,  and  it  may  be 
sufhcient,  here,  merely  to  have  indicated  them. 

The  principle  of  mutation  is  conducive  to  the  assump- 
tion of  distinct  units  in  the  characters  of  plants  and  animals. 
Even  as  chemistry  has  reached  its  present  high  develop- 
ment chiellv  through  the  assumption  of  atoms  and  mole- 
cules as  definite  units,  the  ([ualities  of  which  would  be  meas- 
urable and  could  be  expressed  in  figures,  in  the  same  way 
systematic  botany  and  the  allied  comparative  studies  are 
in  need  of  a  basis  for  measurement  and  calculations.  The 
determination  of  the  degree  of  affinity  now  largely  de])ends 
upon  vague  estimates  and  personal  views;  while,  on  the 
basis  of  the  theory  of  mutations,  the  relationship  is  meas- 
ured by  the  numlx-r  of  the  mutations  which  have  made  the 
forms  under  consideration  different  from  their  common 
ancestors.  The  mutations  themselves  have  evidently  oc- 
curred in  ])revious  times  and  cannot  be  counted  now.  Hut 
if  it  were  })ossible  to  count  their  products,  the  characters, 
the  same  aim  could  be  reached. 

The  study  of  these  unit-characters  may  be  undertaken 
in  three  different  ways:  first,  by  the  production  of  hybrids; 
secondly,  by  the  investigation  of  associated  characters;  and 
in  the  third  place,  by  the  cUrect  observation  of  mutations 
producing  such  units.  In  hybrids  the  characters  of  the  par- 
ents may  be  combined  in  different  ways,  but  the  unit-charac- 
ters connot  be  spht  or  divided.  This  follows  directly  from 
their  definition.  Thus  the  different  combinations  may  lead 
to  the  distinction  of  the  constituents  of  the  mixture.  In  my 
third  chapter  I  shall  deal  with  this  question  on  the  ground  of 
the  experiments  of  Luther  Burbank.  ^  They  afford  a  suffi- 
cient source  of  evidence  to  discuss  this  question  and  are  well 
deserving  of  a  separate  treatment.  On  the  other  hand,  their 
methods  and  scientific  results  are  the  same  as  those  of  the 
European  horticultural  breeders,  as  described  elsewhere. 


Fig.  5-     Lamarck's    Evening-primrose   {Oenothera    Lamarck- 
iana),  a  mutating  species. 


17 


1 8  PLANT-BREEDING 

The  association  of  characters  is  often  called  correlation. 
It  may  be  an  accidental  or  a  normal  coincidence  of  charac- 
ter-units. But  more  often  the  same  simple  character  mani- 
fests itself  in  different  parts  of  the  organism  (as,  for  instance, 
in  the  color  of  flowers,  berries,  seeds  and  fohage)  and  thereby 
affords  a  means  of  investigating  it.  Of  late,  such  associa- 
tions have  become  of  liigh  importance,  since  selection  may 
be  guided  by  them.  Especially,  in  the  isolation  of  new  var- 
ieties of  cereals  has  tliis  use  proven  very  valuable.  Our 
fourth  chapter  will  deal  with  these  questions. 

For  the  direct  observation  of  the  process  of  mutating,  the 
evening  primrose  of  Lamarck  affords,  at  present,  an  un- 
equaled  opportunity.  It  produces  numerous  mutants,  and 
does  so  in  every  generation,  and  almost  any  sample  of  pure 
seed  may  be  used  for  this  study.  This  species  was  described 
by  Lamarck,  from  specimens  of  the  botanical  garden  at  Paris, 
a  century  ago.  It  seems  to  have  since  been  lost.  It  was 
re-introduced  into  European  garden-culture,  about  the  mid- 
dle of  the  last  century,  by  a  nurseryman  in  London,  who 
received  the  seed,  without  name  and  in  a  mixed  packet,  cul- 
tivated and  multiphed  it  and  sold  it  to  the  leading  firms  on 
the  continent.  Ah  the  strains  derived  from  this  scource 
show  the  same  phenomena  of  mutability,  as  far  as  my  experi- 
ments go.  \Vhere  the  species  is  growing  in  America  in  the 
wild  condition,  is  not  known,  at  present,  and  so  it  is  impossible 
to  decide  whether  it  has  acciuired  the  habit  of  mutating  in 
that  condition  or  upon  its  introduction  into  European  culture. 

Twenty  years  ago,  I  found  this  species  on  a  waste  field 
near  Hilversum,  in  Holland,  where  it  had  escaped  from  culti- 
vation and  was  rapidly  multiplying  itself.  Here  it  had  pro- 
duced two  new  and  distinct  varieties  which,  up  to  the  present 
time,  have  not  been  collected  or  observed  elsewhere.  One 
of  them  had  smooth  leaves,  lacking  the  bubbles  of  the  ordi- 
nary form;  it  was  a  fine  type  with  narrower  leaves  and  petals, 


Fig.  6.     Leaves  of  Lamarck's    Evening-primrose   (A),   and  of   two    of   its 
mutants.     B.   Oen.  lata.     C.   Ocn.  scintillans. 


19 


20  PLANT-BREEDING 

the  latter  often  becoming  ovate  instead  of  cordate.  The 
other  had  very  short  styles,  the  stigma  reaching  only  to  the 
mouth  of  the  flower-tube,  instead  of  being  Hfted  up  above 
the  anthers.  Its  ovary  is  only  partly  inferior,  and  it  ripens 
only  very  few  seeds  in  its  capsules,  wliich  remain  small.  It 
has,  moreover,  some  associated  characters  in  its  foUage  by 
which  it  may  be  recognized  before  the  flowering-period.  In 
my  cultures,  both  these  varieties  were  found  to  be  constant 
and  pure  from  seed.  Some  further  mutations  ha^•e  been 
produced  on  the  same  field,  but  since  they  were  also  produced 
in  my  experiment-garden,  I  shall  not  here  mention  them 
separately. 

In  the  year  1886,  I  collected  some  seed  from  the  normal 
plants  of  this  field  and  sowed  them  in  my  garden  the  next 
spring.  This  culture  at  once  gave  a  new  mutation  wholly 
unobserved  until  that  time.  Three  individuals  diverged 
from  the  average,  and  all  three  in  the  same  way.  They  con- 
stituted a  new  type  which  has  been  called  OEnothera  lata  or 
the  broad-leaved  evening  primrose.  Its  leaves  have  rounded 
tips,  its  stems  are  weak  and  bencUng  and  scarcely  reach  half 
the  size  of  those  of  Lamarck 's  primrose.  It  has  thick  flower- 
buds  and  produces  flowers  the  petals  of  which  often  cannot 
completely  flatten  themselves.  The  anthers  are  barren  of 
pollen,  dry  and  twisted.  Its  ovary,  however,  is  normal  and 
can  easily  be  fertiUzed  by  the  pollen  of  the  parent  species. 
In  doing  so  the  next  generation  is,  of  course,  of  hybrid  origin, 
but  it  does  not  produce  intermediates  but  consists  of  some 
typical  CEnothera  lata  and  some  normal  Qlnotheni  Lamarck- 
iana.  By  repeating  the  cross  the  lata  type  maybe  kept  indefi- 
nitely, occurring  in  about  the  same  numerical  proportion 
in   each   generation. 

Starting  from  these  mutations,  I  began  a  regular  scientiflc 
pedigree  culture  of  Lamarck's  evening  primrose,  fertilizing 
the  flowers  artificially  with  their  own  pollen,  protecting  them 


Fig.  7.  IMutants  of  the  Evening-primrose.  A.  The 
red-veined  form  (O.  riibrinervis),  which  is  of  the  same 
size  as  the  original  species.  B  and  C.  The  dwarfish 
variety  {Oen.  nuuella). 


22  PLANT-BREEDING 

from  the  visits  of  insects  by  paper  bags  and  sowing,  each 
year,  the  seeds  of  some  few  normal  individuals  of  the  race 
Tliis  pedigree  embraces,  now,  about  a  dozen  generations, 
the  first  few  of  which  were  biennial,  but  the  later  annual. 
From  tliis  stock  of  normal  plants  it  has  regularly  repeated  its 
first  mutation,  producing  some  latas  in  almost  every  genera- 
tion. The  number  of  these  mutants  was,  on  the  average, 
about  i^  per  cent,  the  mutants  themselves  being  always  alike. 

Moreover,  my  pedigree  culture  has  produced  quite  a 
number  of  other  mutants.  The  most  frec|uent  among  them 
is  a  dwarfish  variety,  the  first  flowers  of  which  open  when  the 
stem  is  only  some  few  inches  high.  It  is  called  CEnothcra 
nanella  and  occurs  as  frecpiently  as  the  CEnothera  lata.  It 
is  completely  fertile  and  produces  an  abundance  of  seeds,  all 
of  which  give  the  same  dwarf  type,  without  ever  reverting  to 
the  high  stature  of  tlie  parent  species.  I  have  cultivated 
these  dwarfs  during  five,  and  more,  generations  and  have 
found  them  true  to  their  type. 

The  first  generations  of  my  pecHgree  culture  had  to  meet 
with  all  the  difficulties  of  a  new  experiment  with  unknown 
and  partly  unsuspected  results.  Accordingly,  they  yielded 
only  a  small  number  of  mutants.  i\s  soon  as  the  method  had 
been  elaborated,  this  number  rapidly  increased.  In  the 
si)ring  of  1895  I  sowed  seed  enough  to  have  about  14,000 
young  seedUng  plants,  which  T  cultivated  until  they  clearly 
showed  whether  they  would  mutate  or  not.  The  mutating 
indiAiduals  were  than  isolated  and  grown  under  very  favor- 
able conditions,  but  of  the  normal  plants  the  larger  part  were 
destroyed.  All  in  all,  I  isolated  60  dwarfs  and  73  lata  and 
five  wholly  different  new  types.  Two  of  them  were  rare,  one 
having  been  found  only  in  one  (O.  gigas)and  the  other  in  two 
individuals  (O.  leptocarpa).  Two  others  were  less  rare,  the 
rubrinervis  appearing  in  eight,  and  the  albida  in  fifteen  speci- 
mens.    The  fifth  was  the  most  frequent  of  them  all,  spring 


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Fig.  8.     A  flowerspike  of  the  giant  mutant  {^Oenothera  gigas),  which  origi- 
nated in  my  garden,  1896, 


23 


24  PLANT-BREEDING 

ing  from  the  main  stem  of  the  Lamarckiana  in  176  of  the 
14,000  seedlings.  It  was  called  oblonga.  All  these  forms 
were  purely  self-fertilized  and  yielded  uniform  races  without 
reversion  to  the  original  evening  primrose  of  Lamarck. 

With  the  exception  of  the  gigas,  which  has  not  been  re- 
peated in  this  pedigree,  all  the  types  spring  more  or  less  regu- 
larly, in  every  generation,  from  the  pure  parent  stock.  As 
often  as  they  were  purely  fertihzed  they  produced  constant 
strains,  which,  however,  did  not  differ  from  the  previous  races 
of  the  same  name. 

Besides  these,  cjuite  a  number  of  minor  mutations  have 
occurred  in  my  cultures.  Some  of  them  died  in  early  youth  or 
before  flowering;  others  were  barren  of  pollen,  or  not  capable 
of  fertilization,  and  yielded  no  seeds.  Some  were  too  weak 
for  the  conditions  of  my  garden  and  succumbed,  sooner  or 
later,  mostly  during  the  winter  after  their  germination.  The 
range  of  mutability  of  this  primrose,  evidently,  has  not  been 
exhausted;  and  even  during  last  summer  a  wholly  new  type 
made  its  appearance. 

A  main  point  in  these  observations  is  that  the  mutations 
occur  suddenly,  without  preparation  and  witliout  interme- 
diates. Xotliing  indicates  on  the  normal  i)lants  what  their 
seeds  will  produce,  and  there  is  even  no  means  at  all  by  which 
to  decide  beforehand  whether  the  fruit  of  one  individual,  or 
one  branch,  will  Ijc  richer  than  any  other  in  the  production 
of  mutations  or  of  some  distinct  mutant.  The  distribution 
of  mutating  seeds  seems  to  depend  simply  upon  chance.  Nor 
are  there  intermediates.  Each  mutant  is  as  good  a  repre- 
sentative of  its  type  as  its  progeny  will  be;  it  does  not  need 
any  special  cultivation  or  improvement  to  reach  the  full  dis- 
play of  its  character.  No  half-mutants  are  seen,  neither 
from  seed  of  the  parent  form  nor  from  seed  of  the  first  mu- 
tant itself.  These  sharp  distinctions  clearly  indicate  that 
each  mutation  consists  of  the  production  of  a  single  unit- 

nonimr  library 

N.  C.  State  College 


25 


26  PLANT-BREEDING 

character;  because,  if  the  characters  were  compound,  they 
would  spHt,  from  time  to  time,  and  be  divided  into  their  con- 
stituents. By  this  means  a  method  is  given  of  studying  the 
expressions  which  the  same  unit-character  may  assume  in  the 
different  organs  of  a  plant.  But  this  point  will  be  more 
closely  studied   in   another   chapter. 

The  question  now  arises,  whether  it  must  be  supposed 
that  species  in  nature  ordinarily  originate  in  the  same  way 
as  in  the  case  of  the  evening  primroses.  Of  course,  the  de- 
tails of  the  process  will  be  different  in  different  cases.  The 
number  of  the  new  types  and  the  frecpiency  of  the  mutating 
individuals  in  each  will  differ;  sometimes  they  may,  perhaps, 
be  more  rare  and,  in  other  instances,  more  crowded.  Other 
differences  there  will,  also,  be.  The  main  point  is,  knvever, 
that  mutations  occur  suddenly  and  by  leaps.  One  genera- 
tion is  sufficien.t  to  produce  the  whole  new  type.  This  is  a 
manifest  contrast  with  the  prevailing  conception  of  slow  and 
almost  invisible  changes  pnxkicing  new  species.  It  may 
shorten  tlie  geological  time  recpiired  for  the  evolution  of 
the  whole  living  world  and  bring  it  witliin  the  Umits  derived 
from  physical  and  astronomical  evidence.  Thus  the  theory 
of  mutation  satisfies  these  demands. 

The  cases  observed  in  horticulture,  the  constancy  of  wild 
species,  the  behavior  of  characters  in  crosses,  the  occurrence 
of  shar])l}'  defined  small  species  within  the  ordinar}-  species 
of  wild  plants  and  even  of  agricultural  crops,  and  many  other 
groups  of  facts,  lead  to  the  same  conclusion.  On  the  other 
hand,  the  slow  change  of  one  species  into  another  has  not,  as 
yet,  been  })roven  in  any  distinct  and  clear  case.  Therefore, 
we  may  assume  that  the  mass  of  the  present  evidence  points 
to  the  conclusion  that  species  originate  laterally  from  other 
species,  by  sudden  leaps.     These  leaps  we  call  mutations. 


Fig.  lo      Dr.  Hjalmar  Nilsson,  Director  of  the  Swedish  Agricultural  Ex- 
periment Station  at  Svalof. 


28 


11. 

THE   DISCOVERY   OF   THE   ELEMENTARY 

SPECIES   OF  AGRICULTURAL   PLANTS 

BY   HJALMAR  NILSSON. 

A.      DIFFERENT  PRINCIPLES  IN  THE  BREEDING  OF 
CEREALS. 

From  the  beginning  of  civilization,  the  cereals  have  taken 
a  prominent  place  in  human  culture.  No  industry  has  been 
so  intimately  connected  with  the  interests  of  mankind,  and 
upon  no  other  agricultural  crop  has  progress  been  so  largely 
dependent.  Long  before  the  time  of  the  ancient  Egyptian 
kings,  of  the  Romans  and  of  the  lake-dwellings  of  central 
Europe,  the  cereals  yielded  the  principal  nourishment  in  all 
the  countries  of  the  world  where  civilization  developed  itself. 
Solms-Laubach  has  pointed  out  that  China  and  Egypt  have 
cultivated  mainly  the  same  species  and  sub-species  of  grains, 
and  that  on  this  ground  it  must  be  conceded  that  their  cul- 
tures have  had  a  common  starting-point.  Three  or  four 
thousand  years  before  Christ,  the  principal  varieties  must 
have  been  known  to  mankind,  and  it  may  even  be  assumed 
that  the  very  first  beginning  of  this  culture  is  much  older. 
Its  probable  origin  is  the  central  part  of  Asia,  since  only  this 
region  can  have  been  its  common  source  for  the  Chinese  and 
Egyptians. 

Having  so  deep  a  significance,  the  cereals  must  have  been 
given  more  attention  and  more  care  than  any  other  crop. 
According  to  some  verses  of  Mrgil,  the  Romans  knew  their 
cultivated  races  to  be  far  from  pure  and  uniform.  They 
also  knew  that  care  had  to  be  taken  in  the  harvesting  of  the 
grains  destined  for  sowing,  since  otherwise  the  races  would 
surely  deteriorate.  Each  year  the  best  ears  had  to  be  selected 
in  order  to  keep  the  varieties  pure  from  an  overwhelming 


30 


PLANT-BREEDING 


Fig.  XI.     Poland  wheat 
{Triticum  polonicum) . 


increase  of   the  unavoidable  admix- 
tures of  little  worth. 

During  the  middle  ages  no  records 
seem  to  have  been  made  as  to  the 
methods  of  cultivating  cereals.  Wheat 
and  barley  had  been  the  grains  of  the 
ancients;  to  these,  oats  have  been 
added  during  the  period  of  the  lake- 
dwellings,  and  rye  is  the  most  recent 
of  the  European  species,  having  been 
introduced  into  Europe  during  the 
middle  ages.  Corn,  of  course,  is  of 
American  origin,  and  has  been  con- 
nected with  the  development  of  the 
ancient  American  cultures,  quite  in 
the  same  way  as  the  grains  were  con- 
nected with  those  of  the  old  world. 

The  idea  of  improving  these  valu- 
abk'  crops  seems  to  have  presented 
itself  only  after  the  beginning  of  the 
last  century.  Different  principles 
were  set  forth,  as  soon  as  the  possi- 
biht}'  of  improvement  had  once  been 
ascertained.  Some  of  them  were  of 
a  more  practical  nature,  resting  on 
direct  observation,  but  others  relied 
on  theoretical  views  concerning  the 
influence  of  environment  on  the  (|ual- 
ities  of  Uving  organisms.  Both  of 
these  main  directions  have  attained  a 
high  degree  of  significance  in  agri- 
cultural practice  as  well  as  in  the 
purely  scientific  discussions  concern- 
ing the  origin  of   species  in   nature. 


NILSSON'S   DISCOVERY  31 

English  breeders  have,  as  a  rule,  preferred  the  more  practical 
line  of  worlving,  but  their  results  have  been  isolated,  and  have 
not  been  combined  into  a  dctmite  system.  German  breeders, 
on  the  other  hand,  liave  followed  the  theoretical  principle 
of  slow  amelioration,  and  have  developed  this  idea  into  a 
broad  system,  which  has  been  applied  by  several  of  their  most 
prominent  men  to  the  improvement  of  numerous  varieties. 

Darwin,  as  is  generally  known,  chose  the  principle  of 
slow  and  gradual  changes  as  affording  the  most  reUable 
facts  for  his  discussion  of  the  manner  in  which  species  are 
produced  in  nature.  In  doing  so,  he  has  brought  the  Ger- 
man method  to  the  rank  of  a  scientific  principle  and  secured 
for  it  the  interest  of  the  students  of  biology  at  large,  but  has 
almost  thrown  into  obHvion  the  other  side  of  the  question. 

Of  late,  however,  new  facts  have  been  discovered,  which 
are  of  a  nature  to  change  the  whole  aspect  of  this  part  of 
the  science  of  evolution.  At  the  Agricultural  Experiment 
Station  of  Sweden,  at  Svalof,  the  German  method  has  been 
extensively  tested,  and  the  result  has  not  been  favorable  to 
it.  New  discoveries  have  been  made  which  go  to  prove  that 
the  whole  principle  of  gradual  changes  rests  on  an  insufficient 
knowledge  of  the  laws  of  variability  of  agricultural  plants, 
and  may  be  replaced  by  more  simple  and  more  direct  methods 
as  soon  as  these  laws  are  exactly  studied.  It  is  my  object  to 
give  a  survey  of  the  deep  significance  of  these  Svalof  experi- 
ments, partly  in  their  practical  bearing  on  agricultural  plant 
breeding,  but  mainly  in  their  complete  compliance  with  the 
doctrine  of  elementary  species,  and  in  their  appreciation  of 
these  as  the  true  material  from  which  selection  has  to  make 
its  choice.  I  shall  endeavor  to  point  out  that  these  new  dis- 
coveries must  deprive  the  principle  of  gradual  ameliorations 
of  its  present  high  rank  in  agricultural  practice,  as  well  as 
of  its  significance  as  a  support  for  the  prevaiHng  views  con- 
cerning the  origin  of  species  in  nature. 


32 


PLANT-BREEDING 


Before  doing  so,  however,  an  historical  sketch  of  the 
principal  methods  and  achievements  of  the  most  renowned 
breeders  of  cereals  may  be  given.     It  will  facihtate   our 


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Fig.  1 2.  A.  Bellevue  de  Talavera-wheat,  isolated  by  Le  Couteur.  B. 
Bearded  white  wheat,  produced  bv  Patrick  Shirreff.  C.  Squarehead 
wheat,  the  most  famous  production  of  the  same  breeder. 


appreciation  of  the  most  essential  features  of  the  wonder- 
ful variabihty  of  these  plants,  and  will  prepare  us  for  an 
unprejudiced  judgment  of  the  opposite  views  concerning  the 


NILSSON'S   DISCOVERY  ^t, 

significance   of  different   kinds   of   variations   for  breeding 
experiments  and  for  scientific  discussions.  — ^ 

Tlie  first  to  discover  tlie  principle  of  improving  cereals 
by  selection  was  the  English  breeder,  Le  Couteur.  He  Uved 
in  the  first  part  of  the  last  century  on  Jersey,  one  of  the 
islands  in  the  Channel,  off  the  coast  of  France.  Once  he 
was  visited  by  Professor  La  Gasca  of  the  University  of 
Madrid,  who,  far  from  admiring  the  purity  and  uniformity 
of  liis  host's  cultures,  pointed  out  to  him  how,  in  reality, 
they  consisted  of  a  mixture  of  more  or  less  easily  recognizable 
types.  He  suggested  the  idea  that  these  types  might  have  a 
chlTerent  share  in  the  harvest  of  the  whole  field,  some  of 
them  being  probably  more  and  others  less  productive  than 
the  average.  _In^  a  field  of  wheat,  he  succeeded  in  distin- 
guishing23_forms,  and  in  other  cultures  similar  indica- 
tions of  variabihty  were  observed.  After  Ms  departure,  Le 
Couteur  saved  the  ears  of  the  indicated  types  separately, 
and  sowed  their  grains  in  small  field  plots  in  order  to  com- 
pare their  productivity.l~He  does  not  seem  to  have  had  any 
theoretical  view  concerning  the  causes  or  the  nature  of  the 
observed  differences,  but  simply  assumed  that  the  progeny 
of  his  selected  plants  would  be  Hke  the  parents.",' On  this 
point  he  soon  found  himself  justified  by  the  results  of  his 
experiments.  He  had  produced  a  group  of  new  types  of 
which  some  proved  better  and  others  less  valuable  than  the 
ordinary  sorts  of  liis  fields.  The  best  new  varieties,  isolated 
in  this  way,  he  then  multiplied,  and  afterwards  put  them 
upon  the  market.  One  of  them  is  still  grown  in  England 
and  the  northern  parts  of  France  on  a  tolerably  large  scale. 
It  is  a  kind  of  wheat  called  "Bellevue  de  Talavera"  and  it 
is  known  to  be  a  very  pure  and  uniform  type.  It  is  so 
uniform  that  it  does  not  afford  any  deviations  by  which  it 
can  be  subjected  to  further  selection,  and  all  trials  in  this 
direction  have  been  in  vain.     Many  breeders  of  later  times 


34  PLANT-BREEDINC; 

have  approached  this  high  degree  of  invariability  in  the  pro- 
ducts of  Le  Couteur's  selection,  and  only  at  present  is  it 
recognized  as  an  instance  of  one  of  the  most  common  laws, 
which  rule  the  phenomena  involved. 

Another  celebrated  breeder  who  worked  on  the  same 
principle,  though  after  a  somewhat  different  method,  was 
the  Scottish  agriculturist,  Patrick  Shirreff.  He  lived  in 
about  the  middle  of  the  nineteenth  centiu^y  and  had  his 
farm  at  Haddington  in  Haddingtonshire.  During  the  first 
period  of  his  work,  he  had  no  iK'tter  conception  concerning 
the  purity  of  his  fields  than  his  contemporaries.  But  he 
observed  that,  from  time  to  time,  and  as  he  thought  by  mere 
accident,  a  plant  occurred  which  seemed  far  more  promis- 
ing than  all  the  remainder  of  the  same  field.  Such  individ- 
uals he  marked,  helping  their  development  by  pulling  out 
their  neighbors  if  they  were  crowded  and  surrounded  them 
by  all  manner  of  attention.  Then  he  saved  their  seeds 
separately  and  sowed  them,  in  order  to  multiply  Ms  new 
types  as  fast  as  possible.  That  such  isolated_indivi duals 
would  yield  a  uniform  progeny  and  become  the  ancestors  of 
constant  races  he  took  for  granted,  and  it  is  very  curious  to 
note  in  his  writings  that  he  did  not  judge  it  worth  while  to 
discuss  this  point,  or  to  state  the  fact  as  he  observed  it. 
His  races  wTre  pure,  and  there  was  no  single  reason  for  him 
to  suggest  that  it  could  have  been  otherwise. 

Shirreff's  exceptional  plants  were  very  rare,  so  rare  even 
that  in  the  first  period  of  nearly  forty  years,  he  succeeded 
in  isolating  only  four  new  varieties  of  prominent  value. 
His  first  discovery  was  made  in  the  year  1819.  He  observed 
a  plant  of  wheat  which  surpassed  its  neighbors  by  its  high 
degree  of  branching.  It  yielded  63  ears  with  about  2500 
kernels.  He  saved  the  seeds,  sowed  them  on  a  separate 
field  and  at  considerable  distances  apart  so  as  to  induce  in 
all  the  plants  the  same  rich  branching.     He  contrived  to 


NILSSON'S   DISCOVERY  35 

multiply  it  so  rapidly  that  it  took  only  two  generations  to  get 
seed  enough  to  bring  it  advantageously  into  the  trade.  He 
gave  it  the  name  of  Mungoswell's  wheat,  and  it  soon  be- 
came one  of  the  most  profitable  varieties  of  Scotland.  It 
has  found  its  way  into  England  and  into  France,  where  it 
is  still  considered  one  of  the  best  sorts  of  wheat. 

It  is  interesting  to  note  that  Shirreff  had  no  idea  of  the 
necessity  or  even  of  the  usefulness  of  a  repeated  selection. 
On  this  point  he  wholly  agreed  with  Le  Couteur.  Without 
exercising  any  choice,  he  sowed  all  the  grains  of  Ms  selected 
plants  and  of  their  progeny,  liis  only  aim  being  to  multiply 
the  new  form  as  quickly  as  possible.  They  yielded  a  uni- 
form race,  and  were  simply  expected  to  do  so. 

Only  five  years  after  his  first  selection,  another  excep- 
tional plant  caught  his  eye.  It  was  an  exceedingly  tall 
individual  in  one  of  his  fields  of  oats.  He  saved  and  sowTd 
its  seeds  separately  as  in  the  previous  case  and  won  a  variety 
which  has  since  been  largely  cultivated  under  the  name  of 
Hopetown  oats.  His  remaining  varieties  were  the  Hope- 
town  wheat,  found  in  1832,  which  was  discovered  and 
multipUed  in  quite  the  same  way,  and  the  Shirrefl"  oats, 
concerning  the  origin  and  treatment  of  which  he  has  not 
judged  it  worth  while  to  give  any  indications.  Both  of 
them  have  gained  a  high  reputation  and  a  widespread 
culture  in  Scotland  as  well  as  in  some  other  European 
countries. 

Until  the  year  1856,  these  four  varieties  were  his  only  im- 
provements. At  that  time,  however,  he  had  acquired  more 
experience  concerning  the  variabihty  of  his  cereals,  and  he 
resolved  to  profit  thereby.  He  had  observed  that  though 
exceptionally  promising  plants  arc  of  course  very  rare,  less 
promising  individuals  may  be  met  with  in  larger  numbers. 
They  would  not  yield  such  excellent  races  as  the  four  men- 
tioned above,  but  notwithstanding  that,   they  might  sulfi- 


36  PLANT-BREEDING 

cicntly  surpass  the  average  to  be  advantageously  selected 
and  cultivated.  The  trials  would  have  to  be  made  on  a 
larger  scale,  and  the  results  would  be  less  striking,  but  on 
the  other  hand,  improvements  could  be  brought  about  in  a 
far  lesser  number  of  years.  Or,  to  state  it  more  correctly, 
the  results  w^ould  no  longer  be  dependent  on  rare  and  casual 
discoveries,  but  would  be  brought  about  systematically. 

He  began  his  selections,  after  this  new  method,  with 
wheat,  and  saved  70  ears  from  different  individuals.  All 
of  them  seemed  to  promise  more  than  the  average  varieties 
of  his  fields.  Of  course  the  kernels  were  sown  separately 
for  each  mother  plant,  and  their  progeny  was  accurately 
tested  and  compared.  As  previously,  he  took  it  for  granted 
that  all  of  these  new  strains  would  be  constant  and  uniform; 
he  observed  the  fact  but  did  not  judge  it  interesting  enough 
to  mention  it  specially.  Among  liis  70  strains  he  chose  at 
the  end  the  three  best  ones,  multipUed  them  as  fast  as  pos- 
sible in  order  to  bring  them  into  the  trade,  and  rejected  all 
the  others.  Those  three  received  the  names  of  Shireff's 
Bearded  Red  Wheat,  Shirreff' s  Bearded  White  Wheat,  and 
Pringle's  Wheat.  For  many  years  they  have  had  a  notable 
place  among  the  best  local  varieties,  and  the  white  variety 
among  them  has  even  found  its  way  into  England  and 
France. 

Having  obtained  these  results  with  wheat,  he  started, 
in  the  year  of  1862,  a  similar  experiment  with  oats.  Four 
of  his  selections  proved  to  excel  the  common  sorts  and  were 
introduced  into  the  trade.  They  bear  the  names  of  Early 
Fellow,  Fine  Fellow,  Long  Fellow,  and  Early  Angus.  Like 
the  wheats,  they  have  been  constant  and  uniform  from  the 
very  beginning. 

Ten  years  afterward,  Shirreff  published  an  account  of 
his  results  and  of  his  methods.  It  was  a  httle  book,  printed 
only  for  private  distribution.     But  it  has  been  translated 


NILSSON'S    DISCOVERY  37 

into  German  by  Dr.  Hcssc  for  the  use  of  the  general  public. 
It  is  largely  devoted  to  the  description  of  the  superior  qual- 
ities of  his  varieties,  and  the  historical  evidence  concerning 
their  origin  is  only  incidentally  given.  From  his  statements, 
we  may  gather  that  at  first  he  assumed  his  mother  plants 
to  be  sports,  but  afterwards  took  them  to  be  simply  old  con- 
stituents of  the  ordinary  cultivated  varieties.  He  observed 
these  to  be  mixtures,  consisting  of  more  and  of  less  abun- 
dantly yielding  types,  and  on  this  observation  founded  the 
method  which  he  followed  during  the  latter  part  of  his  life. 
He  satisfied  himself  that  even  within  these  mixtures  the 
constituents  were  uniform  and  constant  races,  and  there- 
fore it  was  only  natural  that  after  isolation  they  would  re- 
main so.  Shirreff  seems  not  to  have  had  any  idea  of  the 
possibiHty  of  the  existence  of  another  form  of  variability 
as  a  starting  point  for  further  improvement.  Considering 
the  great  importance  which  has  been  conceded  in  Germany 
to  this  possibility,  even  during  the  latter  part  of  Shirreff's 
life,  it  is  not  without  interest  to  lay  some  stress  on  this  fact. 
The  more  so,  since  he  had  in  mind  the  desirabiUty  of  other 
ways  to  reach  the  same  purpose  more  surely  and  more 
quickly.  He  turned  himself  to  hybricUzations  and  made 
some  valuable  experiments  on  the  crossing  of  cereals,  and 
from  his  statements  it  seems  ({uite  evident  that  he  did  so 
only  in  the  firm  conviction  of  having  exhausted  the  possibili- 
ties offered  him  by  variabihty  alone. 

Le  Couteur  and  Patrick  Shirreff  seem  to  be  the  only 
breeders  of  cereals  who  ha\e  worked  on  the  principle  of  one 
single  initial  selection  and  of  subsequent  rapid  multiplica- 
tion without  renewal  of  the  choice  and  without  isolating  the 
best  individuals  during  the  following  generations.  On  this 
point  they  are  to  be  considered  the  precursors  of  the  method 
which  has  of  late  been  discovered  anew,  at  Svalof.  But 
they  had  only  a  very  limited  appreciation  of  the  importance 


38  PLANT-BREEDING 

and  productiveness  of  the  principle  involved  in  their  method 
of  selection. 

At  nearly  the  same  time  with  the  latter  experiments  of 
Shirreff,  another  renowned  breeder  began  to  improve  cereals 
by  selection.  At  Brighton,  in  one  of  the  southern  districts 
of  England,  F.  F.  Hallett  began  his  wT^rk  in  the  year  1857. 
He  seems  to  have  known  the  improved  varieties  of  Le  Couteur 
but  not  those  of  Shirreff.  He  started  from  r^uitc  another 
point  of  view,  which  did  not  rest  upon  the  observation  of 
the  ^'ariability  of  his  grains,  but  was  derived  from  his  previ- 
ous experience  in  tlie  1:) reeding  of  cattle,  especially  in  that  of 
the  short- horns. 

His  principle  was  that  each  plant  has  one  head  which  is 
the  best  of  all  its  ears,  and  that  in  the  same  way  each  ear 
has  one  best  kernel.  Moreover,  he  was  convinced  that  the 
best  kernel  of  the  whole  plant  is  always  to  be  found  in  the 
best  ear.  He  also  assumes  that  the  qualities  of  the  single 
kernels  arc  inherited  \)y  the  plants  wiiich  they  produce. 
From  these  premises  he  concluded  that  varieties  could  be 
improved  by  choosing  the  best  kernel  of  the  best  ear  for 
their  reproduction.  This  choice  had  to  be  repeated  through 
a  series  of  generations,  but  his  experience  taught  him  that 
though  the  gain  was  large  in  the  beginning,  it  did  not  con- 
tinue so,  but  soon  reached  a  limit  which  it  was  practically 
impossible  to  transgress. 

Two  other  features  distinguished  his  work  from  that  of 
Le  Couteur  and  Shirreff.  In  the  first  place,  he  tried  to 
improve  his  plants  directly.  He  satisfied  himself  that  a 
plant,  in  order  to  attain  its  utmost  development,  must  have 
ample  food  at  all  seasons,  and  that  for  this  purpose  not  only 
manure  but  also  depth  of  soil  and  space  were  essential. 
Therefore  he  planted  his  selected  plants  in  a  little  garden 
near  his  house,  gave  them  the  best  garden  soil  and  the 
ordinary  culture  and  treatment  of  garden  plants.     By  this 


Fip;.  13.     A.  Hallett's  pedigree  Chevalier  barley.     B.  Hal- 
Ictt's  pedigree  wheat. 

39 


40 


PLANT-BREEDING 


means  he  increased  the  number  of  their  culms  and  heads 
and  the  number  of  the  spikelets  and  kernels  in  the  individual 
ears.     Twenty  to  lifty  and  more  ears  on  a  plant  of  wheat 


HALLETT'S 
NURSERY  (PEDIGREEl   WHEAT, 


Bred"   upon   lljo    same  princfple    of  REPEATED 

,  races  of  Aalmals. 

STARTINi;    FROM     IINE    l.ri\l\     1>     l_\ni    Y 


SclccUoD  which  has  produced  our  pure 
II  mm  i'kaiis   sictt:s,siVKi.v 


ONE    OF   THE 
ORIGINAL     TWO    EAKS. 


m 


HOW    OITR    WHEAT    CROPS    MAY    BE    DOUBU3>. 


Fig.  14.  A  reproduction  of  part  of  the  first  advertisement  of  pedigree 
wheat  by  F.  F.  Hallctt.  Sec  the  Times,  London,  June  iS,  Nov.  8,  and  Dec. 
19,  1862. 

became  the  rule,  and  ears  with  less  than  80-100  kernels 
were  commonly  rejected.  Tliis  large  increase  can  in  some 
sense  be  called  artificial.  It  appears  as  a  direct  result  of 
the  change  of  culture  and  therefore  came  wholly  or  almost 
wholly  during  the  very  first  year  of  the  selection  experiment. 


NILSSON'S   DISCOVERY  41 

Of  course  the  influence  of  better  nourishment  can  only 
attain  its  liighest  degree  in  the  lapse  of  some  generations, 
since  only  the  very  best  nourished  kernels  will  yield  the 
very  richest  plants.  In  some  cases,  this  process  of  artificial 
amehoration  will  be  rapid,  but  in  others  more  or  less  slow. 
Some  instances  may  be  given.  Hallett's  "Original  Red 
Wheat"  was  started  from  an  ear  containing  47  kernels. 
The  next  generation  yielded  an  ear  of  79  grains,  and  the 
second  came  up  to  go  in  the  richest  car.  During  the  seven- 
teen following  generations,  this  limit  has  practically  not  been 
exceeded,  the  richest  ear  during  all  that  time  having  produced 
only  91  kernels.  In  other  cases  the  development  was  equal- 
ly rapid  in  the  beginning,  but  lasted  during  a  longer  period. 
The  Hunter's  Wheat  began  with  60,  increased  in  the  first 
year  to  90,  and  then  during  some  twelve  years  came  up  to 
106  in  the  best  ear.  The  Victoria  Wheat  began  with  53 
and  slowly  increased  to  loi,  the  gain  of  the  first  generation 
being  only  seven  kernels  for  the  best  ear.  Hallett  assumed 
that  by  this  treatment  the  hereditary  qualities  were  aiiected 
in  the  same  way  as  the  visible  characteristics,  or  in  other 
words,  that  the  varieties  were  directly  improved  by  the  cul- 
ture, the  selection  having  only  the  purpose  of  fixing  the 
acquired  qualities. 

A  second  feature  of  Hallett's  method  was  the  great  care 
bestowed  by  him  on  the  comparison  and  testing  of  his  plants. 
For  each  single  individual,  the  heads  were  counted  and  the 
exact  number  of  kernels  in  each  ear  traced.  These  figures 
were  considered  as  the  main  qualities  according  to  which 
the  plants  were  judged,  and  on  this  ground  the  average 
specimens  and  those  of  minor  worth  could  be  eUminated. 
The  prominent  ones  were  then  brought  to  his  study  and 
minutely  compared  in  all  their  visible  marks.  In  this  way 
the  very  best  specimen  was  isolated,  and  the  same  work 
begun  for  its  culms  and  ears.     Only  one  ear  was  ultimately 


42  PLANT-BREEDING 

chosen  for  the  sowing  of  the  next  generation,  and  this  was 
the  best  on  account  of  its  having  not  only  the  largest  number 
of  kernels,  but  also  the  biggest  and  best  formed  ones  of  them 
all.  Repeatedly  Hallett  has  insisted  upon  the  immense 
amount  of  work  which  this  kind  of  selection  yearly  recjuired. 
This  is  the  more  curious  since  at  the  present  time  hardly 
anybody  attributes  much  importance  to  a  choice  of  the  best 
seeds  on  a  given  individual,  jjrovided  only  that  small  or  un- 
healthy kernels  arc  sufficiently  excluded. 

For  Hallett,  on  the  contrary,  the  choice  of  the  one  best 
kernel  on  the  wliole  plant  was  the  real  aim  in  his  selection. 
He  tried  all  means  for  comparing  the  indivichial  kernels  of 
his  one  superior  ear  with  one  another  and  for  linding  out 
the  best  one.  He  made  investigations  embracing,  on  one 
side,  their  x'isiljle  marks,  and  on  the  other  their  ]>l:ices  on  the 
ear,  those  in  the  middle  part  being  in  the  main  the  better 
ones.  But  he  could  not  discover  distinct  laws  and  so  had 
to  give  up  the  whole  system.  Leaving  aside  all  comparison 
of  the  kernels  of  liis  chosen  head,  he  resolved  to  sow  them 
all  and  to  delay  tlieir  study  until  the  next  generation.  In 
this  he  repeated  his  testing  in  the  manner  described  and 
judging  the  kernels  from  the  pkints  they  had  produced,  he 
was  enabled  to  discern  among  them  the  one  1)y  means  of 
which  he  wished  to  continue  his  race. 

To  this  method  of  selecting  each  year  the  best  kernel  on 
the  best  ear  of  the  best  ])lant,  Hallett  has  given  the  name 
of  pedigree-culture.  Its  essential  feature  is  the  repeated 
selection.  Some  of  his  varieties  were  given  to  the  trade 
under  the  names  of  pedigree  wheats  and  ])edigree  oats.  Of 
the  latter,  his  "pedigree  white  Canadian  oats"  and  his 
"pedigree  black  Tartarian  oats"  may  here  be  mentioned. 
Both  were  introduced  in  the  year  1862.  He  claimed  that 
his  gradual  amelioration  gave  better  varieties  than  the  princi- 
ple of  the  isolation  of  single  plants.     This  may  be  seen  by 


NILSSON'S    DISCOVERY  43 

the  title  of  the  address  dehvered  by  him  in  London  in  1862, 
in  which  he  first  pubhshed  his  resuhs  and  his  views.  It 
was  entitled,  "On  pedigree  in  wheat  as  a  means  of  increas- 
ing crop."  The  improvement  was  obtained  by  the  increase  of 
the  size  of  the  ears,  their  numlx'r  of  kernels  and  the  size  of 
the  latter.  The  number  of  heads  on  a  plant  he  did  not  con- 
sider as  a  subject  of  selection,  but  rather  assumed  that  it  was 
wholly  determined  l3y  the  relative  distance  between  the  plants 
and  therefore  by  the  space  given  them  in  sowing.  For  him, 
the  productiveness  of  a  field  was  proportional  to  the  yield 
of  the  single  ears. 

Moreover,  he  assumed  that  his  pedigree-races  were  not 
only  to  be  amehorated  but  must  be  kept  up  to  their  highest 
point  of  development  by  continued  selection.  As  soon  as 
selection  ceased,  they  would  return  to  their  original  starting 
point,  and  their  su])eriority  over  the  ordinary  cultivated 
varieties  would  chsappear.  This  assertion  has  a  distinct 
and  deep  significance  in  agricultural  practice,  and  has 
gained  a  great  deal  of  influence  in  the  discussion  of  theoret- 
ical questions  as  well.  For  practice  it  means  that  all  the 
seed  destined  for  sowing  should  be  produced  directly  from 
the  pedigree-stock,  and  that  this  is  to  be  kept  constantly 
under  the  same  conditions  of  treatment  and  sharp  selection. 
The  truth  of  this  assertion  has  been  accepted  by  his  custo- 
mers, and  this  fact  has  left  the  production  of  seed  grain 
almost  entirely  in  his  hands.  It  is  easy  to  see  that  the  gain 
made  by  the  breeder  of  a  new  variety  depends,  for  a  large 
part,  on  the  acceptance  of  this  proposition.  In  the  varieties 
produced  by  Le  Couteur  and  Shirreff,  all  seed  is  of  equal 
value,  provided  the  races  are  kept  pure  and  free  from  admix- 
ture. Any  one  may  multi|)ly  them  with  the  same  success 
as  the  original  breeder,  but  on  Hallett's  principle  all  the 
profit  of  the  production  of  rehable  seed  grain  was  given  into 
the  hands  of  him  who  kept  the  original  pedigree. 


44  PLANT  BREEDING 

I  need  not  now  discuss  the  truth  of  this  assertion,  since 
the  same  principle  has  been  accepted  by  the  German  breeders. 
1  might,  however,  point  out  that  the  real  difference  between 
Hallett's  method  and  that  of  his  two  previously  mentioned 
countrymen  is  to  be  sought  in  the  choice  of  the  starting  points 
of  their  experiments. 

Le  Couteur  and  ShirrelT  have  expressed  themselves 
clearly  on  this  point.  "With  them,  all  depends  upon  the 
first  choice.  What  remains  to  be  done  afterward,  is  only 
the  multiphcation  of  the  progeny  of  the  chosen  plant. 
Hallett,  on  the  other  hand,  is  silent  on  this  most  essential 
question.  Like  them,  he  started,  in  each  single  case,  from 
one  plant,  and  therefore  must  have  made  a  choice  among 
the  ty])es  which  his  fields  afforded  him.  On  Shirreff's 
concei)tion,  this  clioice  must  have  been  the  decisive  jjoint  in 
Hallett's  work,  and  not  the  subscfjuent  selection,  and  that 
this  is  true  may  be  proven  by  his  arguments.  In  the  first 
place,  Hallett  has  brought  into  the  trade  new  and  distinct 
varieties,  and  not  merely  more  ])roduclive  strains  of  the  ordi- 
nary sorts.  This  may  be  seen  by  ihe  names  of  the  forms 
already  cited,  and  to  which  the  very  distinctive  types  of  his 
(jolden  Drop  wheat  and  Chevalier  l)arley  may  be  added. 
]\Ioreover,  it  is  proven  by  the  fact  that  his  varieties  have 
kept  their  place  in  agriculture  at  large  and  are  still  keep- 
ing it,  although  it  is  a  long  time  since  Hallett  himself  dis- 
continued their  pedigree-culture.  They  are  now  known 
to  be  independent  varieties  like  those  of  Le  Couteur  and 
Shirreff. 

A  second  argument  is  given  in  the  fact  that  the  \alue  of 
Hallett's  varieties  is  dependent  on  his  first  choice,  and  that 
if  this  should  prove  a  mistake,  no  subsequent  selection  is 
adequate  to  amend  it.  The  proof  of  this  is  given  by  the 
miscarrying  of  some  of  his  pedigree-cultures.  Of  course, 
most  of  these  cases  he  will  hardlv  have  mentioned,  but  it  is 


NILSSON'S   DISCOVERY  45 

a  well-known  fact  that  his  "Original  Red  Wheat"  after- 
ward proved  to  be  a  failure. 

A  very  remarkable  principle  has  been  introduced  of  late 
into  the  methods  of  improving  cereals  by  two  highly  distin- 
guished breeders.  Working  independently  of  one  another, 
they  have  come  to  the  same  idea,  and  the  ameHorations  they 
have  brought  about  give  proof  of  the  correctnessof  their  views. 
At  the  agricultural  experiment  station  of  Minnesota,  W.  M. 
Hays  has  appUed  it  to  the  improvement  of  wheat,  and  in 
Germany  on  his  farm  at  Petkus  von  Lochow  has  appUed  it 
to  the  selection  of  rye.  The  idea  is  the  judging  of  the  hered- 
itary value  of  a  plant,  not  by  its  own  visible  marks,  but  by 
the  average  value  of  its  progeny.  It  must  be  granted 
that  the  visible  qualities  of  a  plant  are  only  a  very  imper- 
fect basis  of  measurement  of  its  fitness  to  reproduce  these 
quahties  in  its  progeny.  The  direct  study  of  this  progeny 
in  itself  must  be  a  far  more  reUable  guide  in  such  an 
estimate. 

The  new  principle  was  of  course  combined  with  the 
choice  of  single  parent  plants  as  the  starting  points  for  new 
races,  and  in  this  important  feature  it  compHes  with  the 
principles  laid  down  by  the  two  first  English  breeders  whose 
methods  I  have  discussed.  But  with  them  the  first  choice 
was  the  principal  act,  although  Le  Couteur  as  well  as  Shirreff 
in  his  second  method  have  largely  relied  on  the  comparison 
of  the  progeny  of  their  first  selections  and  rejected  all  those 
that  proved  inferior  to  his  expectations. 

In  Minnesota,  the  most  widely  cultivated  varieties  of 
wheat  were  Fife  and  Blue  Stem,  and  both  were  decidedly 
inferior  to  the  ordinary  spring  wheat  varieties  of  other  states. 
However,  they  showed  themselves  to  be  as  impure  as  any 
other  ordinary  sorts,  and  thereby  yielded  material  for  method- 
ical improvement.  Hays  chose  from  among  them  a  con- 
siderable number  of  types,  and  after  sowing  the  seed  of  these 


46  PLANT-BREEDING 

single  mother  plants,  he  compared  their  yielding  capacity 
in  the  next  generation.  In  order  to  have  an  easy  standard 
of  comparison,  he  sowed  a  hundred  kernels  of  each  and 
thence  derived  the  name  ''centgener  power"  for  the  index 
of  productiveness  of  the  single  races  isolated  in  this  way. 
IHe  claims  to  have  obtained  varieties  which,  under  the  same 
culture  and  treatment,  will  yield  lo  to  15  per  cent  more  than 
the  old  unpurified  wheats  of  ^linnesota. 

The  same  principle  of  judging  the  ])arent  jjlant  Ijy  the 
average  value  of  its  progeny,  and  of  founding  selection  on 
this  mark,  has  been  applied  by  von  Lochow  to  rye,  and  it  is 
said  that  his  new  race  of  "Rye  of  Petkus"  as  it  is  called, 
excels  all  the  f)lder  improved  German  kinds  of  rye,  and  that 
even  the  celebrated  rye  of  Schlanstcdt  may  soon  prove  to  be 
surpassed  by  it. 

We  have  gi\en  a  sur\ey  of  the  most  ])rominent  and  most 
renowned  principles  in  the  breecUng  of  cereals,  and  liave 
only  to  complete  our  hst  by  a  description  of  the  method 
followed  by  the  larger  number  of  the  breeders  of  Germany. 
Among  them,  Heine,  Drechsler,  ^Mokry  and  Rimpau  may 
here  be  named.  Their  purpose  was  to  improve  the  ordinary 
varieties  by  continuous  selection,  directed  according  to 
distinct  \'iews  and  requirements.  They  considered  the 
starting  points  of  the  English  breeders  as  accidental  sports 
which  no  doul^t  might  be  made  use  of  with  advantage,  but 
would  only  yield  improvements  of  an  inferior  rank. 

Two  features  are  essential  to  this  German  method. 
First  the  initial  choice,  and  secondly  the  slow  and  gradual 
improvement  by  selection.  In  this  first  choice  they  did  not 
try  to  obtain  deviating  types  and  to  isolate  them  from 
among  the  throng.  Quite  on  the  contrary,  they  selected  the 
best  representatives  of  the  variety  they  wished  to  improve,  in 
order  to  be  sure  to  retain  all  of  its  good  features  in  the  new 
race  and  to  combine  them  with  the  new  characters  which 


NILSSON'S   DISCOVERY  47 

they  thought  it  possible  to  give  them.  Starting  from  this 
point  of  view,  it  was  essential  not  to  begin  with  one  single 
mother  plant,  for  tliis  might  perhaps  possess,  among  those 
qualities  wliich  necessarily  or  at  least  ordinarily  escape  obser- 
vation, some  inferior  ones,  whichj  it  must  be  feared,  might 
destroy  the  whole  effect  of  the  ameUorations  obtained  on 
other  points.  Dependence  on  soil  and  manure,  resistance 
to  disease  and  other  essential  ([uaHties  are  not  so  easily  taken 
into  consideration  when  the  selection  is  performed  only  at  the 
time  of  the  harvest,  as  was  then  the  custom.  In  order  to 
become  as  independent  of  these  as  possible,  the  only  way 
seemed  to  start  with  quite  a  considerable  number  of  indi- 
viduals and  to  rely  on  the  laws  of  chance,  trusting  that  these 
would  keep  all  qualities  in  their  average  state,  except  those 
which  should  be  consciously  subjected  to  selection.  It 
was  this  group  of  incUviduals  that  was  to  be  amehorated. 
A  scheme  of  the  desired  improvements  was  made,  and  each 
year  those  ears  or  panicles  were  selected  wliich  more  fully 
comphed  with  it  than  the  remainder.  The  result  was  a 
slow  progress,  but  it  was  thought  to  be  more  rehable  than  the 
sudden  amehoration  of  the  EngUsh  breeders.  Moreover, 
sudden  improvements  are,  os  a  matter  of  fact,  Hmited  in 
their  degree,  and  even  the  pedigree-cultures  of  Hallett  did 
not  escape  from  this  objection.  The  German  principle 
w^as  assumed  to  be  unhmited,  progress  along  the  prescribed 
lines  seeming  to  be  always  possible. 

As  pointed  out  in  the  beginning,  Darwin  has,  in  large 
part,  founded  his  theory  of  the  slow  and  gradual  change 
by  which  the  species  of  plants  and  animals  are  transformed 
into  one  another,  on  the  views  of  the  German  breeders  of 
his  time.  For  tliis  reason  we  shall  have  to  subject  their 
principles  to  an  elaborate  criticism  and  the  short  indication 
given  may  therefore  be  sufficient  for  our  present  purpose. 

The   most   general   conclusion   to   which   our   historical 


48  PLANT-BREEDING 

sketch  has  led  us  is  obviously  that  by  very  dilTcrent  methods 
and  under  the  intluencc  of  widely  divergent  theoretical 
premises,  eciually  good  improvements  have  been  obtained. 
We  may  add  that  even  in  the  number  of  new  and  useful 
varieties  produced,  no  single  one  among  these  methods  evi- 
dently excels  the  others.  It  is  always  a  small  number,  not 
exceeding  ten  or  perhaps  twenty  novelties  in  each  single 
instance,  and  orcUnarily  even  far  less.  Thus  all  these  princi- 
ples are  seen  to  have  only  a  hmited  apphcation,  and  perhaps 
failures  have  been  more  numerous  than  successes  althoufrh 
as  a  rule  only  the  latter  have  been  recorded.  Hence  we  may 
conclude  that  our  knowledge  of  the  variability  of  cereals 
is  not  yet  sufficient  to  enable  us  to  exhaust  all  of  its  possibiU- 
ties,  or  at  least  that  such  a  knowledge  was  not  in  the  posses- 
sion of  the  breeders  whose  great  achievements  have  given 
the  material  for  our  present  sketch. 

B.       THE  SWEDISH  AGRICULTURAL  EXPERIMENT  STATION 
AT    SVALOF. 

During  the  last  twenty  years,  experiments  in  the  Ijreed- 
ing  of  cereals  and  other  agricultural  crops  have  been  con- 
ducted on  an  unusually  large  scale  at  the  Swedish  experiment 
station  of  Svalof.  Considered  from  a  practical  point  of  view, 
they  ha^■e  produced  cjuite  an  astonishing  numljer  of  new 
races,  by  which  agriculture  in  almost  all  the  districts  of 
Sweden  has  been  greatly  improved,  and  which  are  now  at- 
tracting the  attention  of  numerous  agriculturists  in  other 
countries.  Their  methods  took  their  origin  from  those  fol- 
lowed in  Germany,  but  were  soon  changed,  and  may,  at 
present,  be  more  closely  compared  with  the  work  of  Le  Cou- 
teur  and  Shirreff,  though  developed  quite  independently 
of  these  men,  whose  ideas  were,  at  that  time,  only  locally 
appreciated. 

For  the  students  of  the  problems  of  evolution,  the  methods 


49 


50  PLANT-BREEDING 

and  the  results  of  the  Svalof  station  have  a  very  deep  signifi- 
cance. They  contirm  the  fact  that  the  ordinary  cultivated 
varieties  of  cereals  are  by  no  means  pure,  but  must  be  con- 
sidered as  mixtures  of  well  defined  types.  Moreover,  they 
show  that  these  types  are  far  more  numerous  than  was  pre- 
viously supposed,  and  include  hundreds  of  forms  within  each 
of  the  now  prevailing  sorts.  They  also  show  that  the  differ- 
ences among  these  newly  discovered  elementary  types  arc 
far  greater  than  might  be  suspected  from  the  study  of  the 
varieties  isolated  by  other  breeders.  The  range  of  variabil- 
ity disclosed  by  these  new  studies  is  simply  so  wide  that  it 
affords  all  the  re(|uired  material  for  almost  all  the  selections 
desirable  at  present,  and  will  no  doubt  continue  to  be  an 
inexhaustible  source  of  im])rovements  for  a  long  succession 
of  years.  They  are  founded  on  the  ])rinci])le  of  single  selec- 
tions, and  the  range  of  appHcation  of  this  method  is  pro\en 
to  be  so  extensive  as  to  make  all  ideas  of  repeated  or  con- 
tinuous selection  simply  superfluous.  It  is  even  so  rich  in 
its  productiveness  tliat  there  is  scarcely  any  room  left  for 
other  methods  of  improvement;  and  especially  should  all 
endeavors  of  winning  ameHoratcd  varieties  of  cereals  by 
means  of  hyl)ridi/.ation  simply  be  left  out  of  consideration, 
as  compared  with  the  immense  number  of  more  easily  pro- 
duced novelties  which  this  method  offers. 

Leaving  the  teachings  which  may  be  derived  from  this 
work  in  the  study  of  the  evolution  of  the  organic  world  for 
another  chapter,  I  shall  now  tr\-  to  give  an  idea  of  the  work 
itself.  This  may  be  divided  into  two  parts;  the  first  com- 
prising the  use  and  criticism  of  the  German  method,  and 
the  second  embracing  the  discover}^  and  application  of  the 
principle  of  selecting  elementary  species. 

Some  historical  details  may  precede  this  discussion. 
Svalof  is  a  little  village  in  the  Swedish  province  of  Schonen, 
situated  in   the   neighborhood   of  Helsingborg,   Lund  and 


NILSSON'S   DISCOVERY  51 

Malmo,  close  to  the  southwestern  shore,  and  opposite  Co- 
penhagen in  Denmark.  In  this  village,  a  company  for  the 
production  and  improvement  of  seed-grains  for  the  southern 
part  of  Sweden  was  organized  in  the  year  1886.  Its  aim 
was  the  procuring  and  testing  of  new  and  foreign  varieties 
of  agricultural  crops,  in  order  to  replace  the  Swedish  sorts, 
which  at  that  time  were  slowly  but  manifestly  deteriorating. 
This  deterioration  was  discovered  to  be  a  consequence  of 
the  multiplication  of  admixtures  of  less  value,  which,  though 
rare  and  unobjectionable  in  the  countries  whence  the  vari- 
eties were  derived,  were  seen  to  thrive  in  a  most  obnoxious 
way  under  the  influence  of  the  Swedish  soil  and  climate, 
and  to  lessen  the  value  of  the  harvest  in  an  important  degree. 
To  procure  new  samples  of  seed  grains  was  the  first  way  of 
combating  this  evil,  the  second  being  the  purifying  of  the 
introduced  supplies  before  giving  them  into  the  hands  of 
the  Swedish  farmers.  This  cleaning  could  be  performed 
partly  in  the  imported  samples  themselves,  but  had  to  be 
combined  also  with  the  culture  and  multiplication  wliich 
usually  precede  the  sale. 

The  company  was  founded  by  private  agriculturists  and 
had  consequently  to  serve  only  the  needs  of  practice.  All 
educational  aims  and  purel}-  scientific  researches  are  ex- 
cluded from  its  program,  but,  on  the  other  hand,  its  work  is 
based  on  exact  scientific  methods.  Its  botanical  studies 
are  as  broad  as  possible,  but  always  in  the  direct  service  of 
agricultural  practice.  In  this  respect  it  is  to  be  sharply  con- 
trasted with  most  of  the  experiment  stations  of  Europe  and 
America,  and  it  is  important  to  state  that  exactly  through 
this  procedure  the  obtained  results  have  come  to  be  of  ex- 
ceptionally great  significance  for  science  as  well  as  for  prac- 
tice. Another  consequence  of  this  essential  feature  of  the 
program  is  that  its  publications  are  destined  only  for  the 
farmers  of  Sweden.     They  are  pubUshed  in  the  Swedish 


52  PLANT-BREEDING 

language  and  deal  with  tlic  results  (^f  the  work.  Fortu- 
nately, however,  the  Director  and  his  staff  have,  from 
time  to  time,  given  short  surveys  of  the  progress  realized, 
and  of  the  methods  followed  in  securing  these  practical 
results. 

One  of  the  means  by  which  the  young  company  contrived 
to  gain  a  notable  influence  over  Swedish  agriculture,  was 
by  increasing  the  interest  of  the  farmers  in  the  purity  and 
the  control  of  their  seed  grains.  Exhibitions  and  distribu- 
tions of  samples  of  pure  seeds,  descriptions  of  the  various 
marks  by  which  the  varieties  may  be  recognized,  repeated 
inspections  of  the  fields  of  the  station,  where  pure  cultures 
were  grown  side  by  side  with  the  common  Swedish  sorts, 
gradually  convinced  the  farmers  of  the  great  significance 
attached  to  the  careful  choice  of  their  sowing-seeds.  As 
soon  as  this  conviction  Ijecame  general,  the  results  could  no 
longer  remain  doubtful,  and,  gradually,  the  fame  of  the 
station  increased  to  a  degree  corresponding  with  the  aug- 
mentation of  the  harvest. 

This  purification  of  the  imported  strains  must  evidently 
lead  to  an  exact  study  of  the  constituents  of  the  original  mix- 
tures and  to  a  comparison  of  the  part  they  take  in  the  harvest. 
In  the  beginning,  however,  these  were  wholly  obscured  by 
the  views  which  were  then  prevalent  in  Germany  concerning 
the  improvement  of  races  among  agricultural  plants.  It 
was  taken  for  granted  that  the  ])urification  of  the  imported 
samples  was  simply  to  make  them  true  representatives  of  the 
variety  under  the  name  of  which  they  had  been  bought, 
so  as  to  guarantee  their  ([uaHty  to  the  Swedish  purchasers. 
Furthermore,  it  was  desired  to  accHmatize  the  best  foreign 
kinds  and  to  make  them  suitable  to  the  requirements  of  the 
soils  and  climates  of  Sweden  as  well  as  to  the  various  de- 
mands of  the  local  industries.  This  part  of  the  program, 
however,  was   intended   as  an  application  of   the   German 


53 


54  PLANT-BREEDING 

methods  of  improvements  to  the  special  needs  of  Swedish 
agricuhure. 

From  these  statements  it  may  easily  be  gathered  that  the 
importation  of  new  and  valuable  kinds  from  neighboring 
countries  was,  at  first,  one  of  the  chief  occu})ations  of  the 
station.  The  most  prominent  and  most  renowned  varieties 
of  the  cereals  of  Europe  were  purchased  and  tested,  the  old 
and  common  sorts  as  well  as  the  newly  introduced  and  ameli- 
orated kinds.  After  fmding  them  ade([uate  to  the  local  cir- 
cumstances, they  were  multipHed,  exhibited  and  recommen- 
ded and  hnally  given  to  the  trade.  In  this  way,  Prol)steier 
oats,  Tigowo  oats,  S(|uarehead  wheat,  \'ictoria  ]x>as  and 
different  kinds  of  barley  have  been  distributed.  By  their 
culture,  the  agriculture  of  the  southern  parts  of  Sweden  was 
noticeably  improved,  and  even  the  export  of  grains  to  Bel- 
gium and  other  Kuro])ean  coimtries,  which  previously  had 
suffered  much  from  the  deterioration  of  the  races,  could  be 
restored  to  its  former  degree  of  importance. 

The  influence  of  these  new  methods  may  best  be  judged 
by  the  rapid  growth  of  the  company.  Already  in  the  second 
year,  it  could  extend  its  interests,  which  were  primarily  in- 
tended for  the  southern  part  of  Sweden  only,  to  the  whole 
countrv.  Soon  afterwards,  another  company  was  organ- 
ized on  the  same  principles  and  with  the  same  aims.  It  had 
its  seat  at  Orebro  and  was  destined  to  work  for  the  middle 
part  of  Sweden.  But  after  an  existence  of  only  four  years, 
it  was  combined  with  the  Svalof  company,  which  then  (1894) 
took  its  present  name  of  Sveriges  Utsadesforening,  or  Seed- 
grain  Society  for  Sweden.  It  entered  into  relationship  with 
the  greater  number  of  local  agricultural  companies  and  was 
financially  aided  by  them  as  well  as  by  the  Swedish  govern- 
ment, so  as  to  be  enabled  to  work  on  a  largely  increased  scale. 

Gradually  the  combination  of  the  experimental  and  the 
commercial  sides  of  the  work  became  too  cumbersome,  and 


NILSSON'S   DISCOVERY  55 

moreover  brought  about  a  kind  of  competition  with  the  local 
seed  dealers,  which  was  felt  to  be  a  hindrance  to  its  further 
development.  Five  years  after  its  establishment  (i8gi) 
these  considerations  led  to  a  separation  of  the  two  branches, 
a  separate  company  for  the  sale  of  the  improved  grains  being 
organized  under  the  name  of  Allmanna  Svenska  Utsadesak- 
tiebolaget  or  General  Seed-grain  Trading  Company  of 
Sweden.  This  company  has  its  seat  at  Svalof,  too,  and  re- 
ceives the  seeds  of  the  ameliorated  varieties  which  the  society 
has  produced,  in  order  to  multiply  and  distribute  them.  It 
is  operated  constantly  under  the  control  of  the  seed-grain 
society  and  thereby  is  enabled  to  keep  its  races  uniform  and 
to  sell  them  under  a  full  guarantee  of  purity. 

Before  leaving  the  history  of  the  experiment  station,  some 
words  should  be  added  concerning  its  means  of  providing 
races  for  different  parts  of  Sweden.  Sweden  embraces  a  wide 
range  of  climates,  from  its  cold  northern  parts  to  the  mild 
and  favorable  clime  of  the  southern  provinces.  ^Moreover, 
there  is  a  large  variety  of  soils.  Hence  it  is  evident  that  the 
production  of  good  cereals  for  all  those  various  parts  can- 
not be  effected  at  one  single  point.  No  variety  can  claim  to 
be  appropriate  for  a  definite  soil  or  climate  before  it  has  been 
tested  under  the  circumstances  for  which  it  is  destined.  The 
work  of  the  society  is  therefore  twofold,  and  the  principle  has 
been  accepted  that  the  varieties  are  produced  at  Svalof,  but 
afterward  sent  to  other  localities,  according  to  their  qualities 
and  their  probability  of  success.  Everywhere  in  the  country, 
the  numerous  local  agricultural  societies  are  co-operating 
with  the  station  of  Svalof  for  tliis  purpose.  As  soon  as  a 
new  race  is  considered  especially  recommendable  for  some 
soil  or  some  chmate,  it  is  sent  to  the  locaUty  in  question  and 
tested  there  by  field  cultures  in  comparison  with  the  local 
sorts.  By  this  means,  many  valuable  improvements  of  local 
cultures  have  been  obtained. 


56  PLANT-BREEDING 

With  the  same  object  in  view,  two  branch  stations  have 
been  organized.  One  of  them  is  situated  at  Lkiina  in  middle 
Sweden,  and  the  other  at  Alnarp  in  the  same  region  but  on  a 
richer  soiL  At  Uhuna,  for  instance,  the  cuUures  of  the  new 
Svalof  Black  Bell  oats  are  attracting  special  attention. 

During  the  first  years  of  its  existence,  the  station  followed 
the  methods  of  selection  and  amelioration  which,  at  that 
time,  were  generally  accepted  by  the  breeders  of  central  Eu- 
rope. As  we  have  seen  in  our  last  lecture,  the  German 
breeders  considered  the  im])urities  of  their  races  as  of  minor 
importance.  They  could  ])v  gotten  rid  of  by  a  careful  choice 
of  the  best  and  most  typical  ears,  and  the  saving  of  seed  for 
sowing  had  of  course  to  be  accompanied  always  by  some  such 
kind  of  selection.  The  exclusion  of  inferior  ears  was  more 
or  less  considered  as  the  necessary  means  of  keeping  the  races 
true  to  tlu'ir  standard  ty])e.  Improved  races,  as  a  rule,  were 
more  responsi^■e  to  soil,  manure  and  treatment  than  the  local 
varieties.  It  is,  however,  unavoidable  that,  with  the  straw 
of  the  manure,  some  stray  grains  of  these  inferior  sorts  will, 
from  time  to  time,  and  not  rarely,  come  onto  the  fields.  Here 
they  will  be  content  with  a  lesser  supply  of  food,  space  and 
care  than  the  improved  races,  and  thereby  be  enabled  to  grow 
faster  and  multiply  more  ciuickly.  It  is  hardly  conceivable 
how  soon  these  inferior  races  may  multiply  themselves  to  such 
an  extent  as  to  occupy  large  parts  of  the  field,  supplanting 
the  ameHorated  type  and  lessening  the  harvest  to  a  noticeable 
degree.  In  bad  years,  even  the  wind  oats  which  scatter 
their  small  seeds  to  the  winds  and  thereby  yield  nothing  at 
all  for  the  harvest,  may  be  seen  to  replace  more  than  half  the 
stock  of  the  fields 

Under  such  circumstances,  keeping  the  races  pure  by 
means  of  selection  is  evidently  a  necessary  part  of  all  intelli- 
gent culture.  It  is  the  first  thing  to  be  done,  but  it  is  consid- 
ered   hardly  worthy    the  name  of  imi)rovement.     In    Ger- 


57 


58  PLANT-BREEDING 

many,  real  improvement  was  treated  as  a  separate  occupation 
and  was  considered  as  requiring  a  large  amount  of  study, 
and  the  devoting  of  oneself  to  a  proposed  aim.  The  gener- 
al custom  was  to  start  such  experiments  from  the  best  local 
or  improved  varieties  by  an  initial  choice  of  a  certain  number 
of  typical  heads.  Such  a  group  of  selected  plants  was 
called  the  elite,  and  this  elite  had  to  be  ameliorated  accord- 
ing to  the  prevaiHng  demands  or  even  simply  in  accordance 
with  some  ideal  model.  Year  after  year,  the  best  ears  of 
the  ehte  group  were  chosen  for  the  continuance  of  the  strain 
or  family,  and  slowly,  but  gradually,  its  quahties  were  seen 
to  improve  in  the  desired  direction.  After  some  years, 
such  a  family  might  become  decidedly  better  than  the  variety 
from  which  it  had  been  derived.  Then  its  yearly  harvest 
would  be  divided  into  two  parts,  after  having  been  sufticiently 
purified  ])y  the  rejection  of  accidental  ears  of  minor  worth. 
The  best  ears  were  carefully  soiight  out  and  laid  aside  for 
the  continuance  of  the  elite  strain,  but  the  remainder  were 
sown  on  a  distant  field  in  order  to  be  multipHed  as  fast  as 
possible.  By  this  means,  after  a  multiplication  during  two 
or  three  generations,  its  product  could  be  used  as  seed  grain 
for  the  farm  or  sold  to  others  for  the  same  purpose.  Each 
year  the  elite  would,  of  course,  give  a  new  and  better  har- 
vest which  could  be  multiphed  and  sold  in  the  same  manner. 
From  tliis  description,  it  may  easily  be  gathered  that  an 
improved  variety,  produced  after  these  principles,  cannot 
be  called  a  race  in  the  ordinar}-  sense  of  the  word.  Only 
the  ehte  itself  is  a  pure  race,  but  it  consists  of  only  a  small 
family,  cultivated  on  a  single  farm.  The  extensive  cultures  of 
the  succeeding  years,  however,  are  not  related  to  one  an- 
other in  the  ordinary  way  of  ancestors  and  descendants. 
They  are,  or  at  least  they  should  be,  the  ends  of  succeeding 
side-branches  of  the  elite,  each  branch  being  surpassed  in 
excellence  by  its  successor,  and  therefore  no  longer  deserv- 


59 


6o  PLANT-BREEDING 

ing  to  be  kept  in  culture.  Since  only  the  elite  can  produce 
the  most  advanced  side-branches,  the  production  of  seed 
grains  has  always  to  return  to  it  or  rather  to  be  started  anew 
from  it.  No  farmer  should  sow  his  own  harvest,  because 
if  he  docs  so,  he  will  soon  be  surpassed  by  others.  Or,  if 
he  should  be  able  to  do  it  without  harm,  it  can  last  only  for  a 
few  years,  since  he  cannot  keep  up  the  selection  which  alone 
is  ade([uate  to  maintain  the  race  at  its  highest  standard. 

Contrary  to  the  opinion  of  Hallett,  who  claimed  to  pro- 
duce his  ameUorations  by  giving  his  plants  large  space, 
ample  manure  and  the  best  possible  exposure  and  treat- 
ment, the  German  j^rinciple  was  to  make  the  selections  under 
precisely  the  same  conditions  as  those  of  the  ordinary  field 
cultures.  It  was  assumed  that  changes  produced  by  the 
outward  conditions  of  life,  were  only  of  a  temporary  and 
and  not  of  an  hereditary  nature.  Hereditary  qualities  were 
assumed  to  be  innate  and  independent  of  environmental 
intluences.  Only  by  means  of  selection  could  they  be  fixed, 
increased  or  lessened,  and  fmally  changed  in  detinite  ways. 
On  the  ground  of  these  views,  selection  was  the  true  factor 
of  the  improvement,  and  since  the  breeder  could  select  ac- 
cording to  his  own  wishes  and  ideals,  it  was  believed  that 
selection  was  a  means  of  changing  any  plant  in  any  direction, 
and  to  any  desirable  degree.  By  direct  changes,  brought 
about  by  local  and  individual  differences  in  the  life  conditions, 
this  selection  could  only  be  misled,  since  such  a  change 
might  be  taken  for  an  hereditary  improvement  whenever  its 
real  cause  was  hidden.  Therefore  it  was  a  rule  to  reject  all 
specimens  which  could  possibly  have  profited  by  an  excep- 
tional amount  of  space,  manure  or  Hght,  before  beginning 
the  real  selection. 

Such  were  the  more  or  less  clearly  understood,  and  more 
or  less  generally  accepted  views  in  central  Euro])e  at  the  tjme 
of  the  estabhshment  of  the  experiment  station  at  Svalof.     No 


NILSSON'S    DISC(3VKRY  6i 

reason  to  doubt  their  validity  was  at  hand,  and  moreover,  the 
cvidenec  was  only  seanty  and  widely  scattered,  without 
affording  sufficient  material  of  facts  for  a  thorough  criticism. 
The  results  of  the  English  breeders  were  hardly  accessible  at 
that  time,  and  so  the  Svalof  experiments  had  to  begin  by 
following  the  German  principle.  Resuming  the  principal 
features,  we  may  state  that  it  commenced  with  the  choice  of 
a  certain  number  of  ears,  and  cultivated  their  progeny  as  a 
mixed  family,  in  which,  year  after  year,  the  best  heads  were 
chosen  in  adequate  number  for  the  continuance  of  the  race.    / 

The  experiment  station  at  Svalof  has  accepted  the  prin- 
ciple that  the  selection  cultures  must  be  made  on  the  same 
soiljinjl  under  the  same  conditions  as  the  ordinary  field  cul- 
tures. Especially,  the  distances  at  which  the  seeds  were 
sown  from  each  other  had  to  l^e  the  same,  this  being  a  point 
which  had  often  been  dealt  with  in  another  way,  since  by  a 
somewhat  larger  relative  distance,  the  treatment  and  the 
final  distinguishing  of  the  single  plants  is  notably  facilitated. 
This  principle  has  been  found  to  be  reliable,  and  has  been 
kept  unchanged  through  all  the  periods  of  experimentation, 
which  have  supplanted  almost  all  others. 

Moreover,  the  methods  of  testing  and  comparing  have 
been  largely  improved.  Instead  of  the  personal  apprecia- 
tion of  the  c[ualities  of  the  ears,  accurate  measurements  have 
been  adopted.  An  elaborate  book-keeping  reciuired  the 
statement  of  a  large  number  of  c[ualities  by  short  indica- 
tions, and  figures  came  to  be  preferred  to  descriptions.  The 
length  of  the  ears  was  given,  their  form  indicated  by  width 
and  breadth,  and  by  the  place  where  both  reached  their  max- 
imum value.  The  density  could  be  measured  by  the  num- 
ber of  nodes  and  spikelets,  and  in  the  latter,  the  number  of 
single  kernels  could  be  noted.  Other  valuable  c|ualities 
recjuired  separate  tools  and  instruments,  and  even  the  degree 
of  brittleness  had  to  be  expressed  by  figures. 


62  PLANT-BREEDING 

By  these  means  it  was  soon  found  possible  to  extend  the 
experiments  to  a  previously  unknown  number,  and,  at  the 
same  time,  to  obtain  far  larger  deviations  from  the  initial 
type  in  a  relatively  short  succession  of  generations.  There- 
by the  breeder  was  enabled  to  collect  his  experience  on  a 
scale  large  enough  to  yield  the  material  for  a  full  experi- 
mental criticism  of  the  whole  method.  The  result  of  this 
part  of  the  work  pro\'ed,  however,  to  be  not  at  all  satis- 
fying. 

Of  course,  the  first  selection  experiments  were  conducted 
according  to  the  local  needs  of  the  farmers.  Among  oats 
the  celel^rated  races  of  the  Probstei  were  cultivated,  among 
the  peas  the  variety  called  Victoria,  and  among  wheat  the 
squarehead  sorts.  Shortly  before,  the  French  breeder,  Vil- 
morin,  had  produced  a  new  variety  of  oats  to  which  he  had 
given  the  name  of  Ligow^o  oats.  It  was  tested  at  Svalof, 
and  its  introduction  into  Swedish  agriculture  has  l)een  one 
of  the  l)est  successes  of  tlie  young  station.  In  the  same  way, 
two  of  the  older  varieties  of  barley,  the  "Plumage"  and  the 
"Prentice,"  were  recommended  and  soon  largely  distrib- 
uted. The  testing  was  always  performed  under  strict  com- 
parison with  the  local  varieties,  of  which,  for  this  reason,  a 
considerable  number  were  kept  in  culture. 

In  the  meantime,  the  deficiencies  of  the  method  could  not 
escape  observation.  All  those  which  were  of  a  purely  tech- 
nical nature  could  be  overcome,  and  on  this  side  of  the 
problem  a  high  degree  of  perfection  was  attained.  But  there 
were  other  weak  points  which  were  related  to  the  very  foun- 
dation principles  of  the  method.  Among  these,  the  principal 
one  was  that  the  continuous  selection  of  the  best  specimens  in 
an  arbitrary  direction  did  not  lead  to  improvement  in  all 
cases.  Quite  on  the  contrary,  success  was  rare;  so  rare, 
even,  that  it  could  almost  be  looked  upon  as  an  exception. 
The  fact  itself  was  not  new,  since  in   Germany,  also,  only 


NILSSON'S   DISCOVERY  63 

in  exceptional  cases  a  real  improvement  had  been  obtained. 
But,  of  course,  usually  only  successful  instances  are  pub- 
lished, and  concerning  the  remainder  ordinarily  no  evidence 
is  at  hand. 

In  Svalof,  however,  where  numerous  experiments  of  the 
same  kind,  but  with  different  varieties  of  cereals,  were  con- 
ducted side  by  side,  the  fact  could  not  escape  observation. 
Soon,  the  idea  suggested  itself  that  if  success  is  an  exception, 
the  principle  involved  in  the  method  can  hardly  be  a  valuable 
one,  at  least,  not  one  on  which  the  breeder  may  confidently 
rely. 

An  instance  may  be  given.  As  such,  I  choose  the  Chev- 
alier barley,  which  is  one  of  the  most  ^'aluable  kinds  for  the 
brewers.  In  Sweden,  it  has  the  defect  of  being  often  ex- 
posed to  lodging  or  lying  down.  The  culms  are  too  weak, 
and  are  thrown  down  by  wind  and  rain  shortly  before  the 
time  of  the  harvest.  Great  losses  are  usually  the  conse- 
quence, and  it  was  considered  a  distinct  necessity  to  breed  a 
Chevalier  barley  with  culms  stiff  enough  to  resist  these  evils, 
even  on  the  hard  soils  of  the  middle  parts  of  Sweden.  Here 
the  culture  of  this  variety  had  been  tried  on  a  large  scale, 
but  wos  given  up  in  consequence  of  the  defect  alluded  to. 
In  order  to  introduce  it  anew,  and  to  restore  the  brewer's 
industry  to  its  former  degree  of  development,  the  Chevalier 
barley  had  to  be  improved  and  adapted  to  the  circumstances. 
This  demand  seemed  the  more  proper,  since  elsewhere  and 
especially  in  Germany,  this  barley  had  attained  the  height 
of  its  renown  exactly  at  that  time.  There  could  not  be  any 
doubt  that  it  was  the  best  kind  for  brewing  purposes.  On 
this  account,  it  was  cultivated  at  Svalof  on  a  large  scale,  and 
with  all  possible  care.  It  was  submitted  to  repeated  selec- 
tion with  the  distinct  purpose  of  giving  it  stiffer  culms.  The 
results,  however,  did  not  correspond  with  the  expectations. 
The  harvest  remained  comparatively  small,  and  the  quality 


64  PLANT-BREEDING 

was  not  that  which  might  be  expected.  The  cuUiires  were 
correspondingly  increased  in  extent,  and  the  selection  made 
more  intense.  The  whole  experiment  was  worked  up  to 
such  a  degree  of  perfection  that  it  could  not  only  be  com- 
pared with  the  most  renowned  German  pedigree  cultures, 
but  might  even  be  considered  as  a  test  by  which  the  value 
of  the  principle  itself  could  be  judged. 

Notwithstanchng  this,  the  result  was  an  absolute  negative. 
It  was  simply  impossible  to  get  rid  of  tlie  propensity  to  lie 
down.  Xo  real  improvement  could  Ijc  reached.  After 
many  years  of  hard  work  with  steadily  improved  instru- 
ments and  methods  of  testing  and  selection,  the  experiment 
had  to  be  given  up,  since  there  was  no  ground  for  the  hope  of 
finally  reaching  the  aim. 

At  the  same  time,  a  considerable  numljcr  of  other  selec- 
tion ex])eriments  had  been  carried  on.  Some  of  them  gave 
the  desired  results,  but  others  did  not.  The  positive  in- 
stances were  only  few,  and  although  they  have  produced 
quite  valuable  new  races,  and  have  distinctly  contril^uted 
to  the  improNement  of  agriculture  in  southern  Sweden,  it  was 
clear  that  they  could  not  afford  sufticient  proof  for  the  reha- 
biUty  of  the  principle. 

Success  remained  an  exception,  and  exceptional  improve- 
ments were  not  the  aim  of  the  work  of  the  station.  Dis- 
tinct problems  it  had  to  solve.  It  had  to  free  the  old  varieties 
from  definite  defects,  which  impeded  their  more  extensive 
use.  A  method  wliich  would  give  its  results  in  some  cases 
and  in  others  not,  could  not  be  considered  as  involving  the 
principle  wanted.  On  the  contrary,  the  conclusion  had  to 
be  granted  that  in  the  positive  cases,  the  result  might  be  due 
to  cjuite  other  causes,  and  that  if  it  were  only  possible  to  dis- 
cover these,  the  whole  system  might  be  thrown  over  and 
replaced  by  sure  and  more  reliable  principles.  The  Ger- 
man idea  that  it  was  in  the  power  of  man  to  improve  his 


NILSSON'S  DISCOVERY  65 

plants  in  an  arbitrarily  chosen  direction,  was  manifestly  con- 
tradicted by  nature.  The  plant  develops  itself  after  its  own 
capacity,  but  does  not  suffer  itself  to  be  forced  into  other 
ways. 

The  principle  of  slow  and  gradual  amelioration  by  so- 
called  methodical  selection  was  thereby  condemned.  The 
squarehead  wheat  showed  itself  to  be  as  Httle  amenable  to 
improvement  as  the  barley.  Even  the  oats  could  not  be  im- 
proved. The  new  varieties  which  were  occasionally  ac- 
quired by  the  process  might  as  well  be  considered  as  accidents. 
Among  them  was  the  Princess  barley,  which  had  been  derived 
from  the  introduced  Prentice  barley,  and  wliich  gained  a 
high  reputation  and  extensive  distribution.  In  the  same 
way,  the  Plumage  barley  yielded  some  valuable  novelties. 
There  was  no  reliabiUty  in  the  method,  nor  could  it  be  dis- 
covered why  a  result  might  be  obtained  in  some  cases,  and 
in  others  not.  It  was  clear  that  the  solution  of  the  great 
problem  was  to  be  sought  in  cpiitc  another  way. 

In  the  next  chapter  I  propose  to  deal  with  the  further 
experiments  of  the  station  at  Svalof,  which  led  to  the  dis- 
covery of  the  principle  that  the  elementary  species  are  the 
true  material  for  selection,  and  that  they  are  numerous  and 
varied  enough  to  satisfy  all  the  present  demands  of  practice. 
In  order  to  make  this  description  independent  of  all  dis- 
cussions of  the  older  principle,  I  will  once  more  point  out 
the  essential  differences  between  the  German  method  and 
the  work  of  the  previous  English  breeders,  as  described  in  the 
former  chapter.  In  doing  so  we  have  to  exclude  the  views 
of  Hallett,  who  partly  participated  in  the  ideas  of  his  coun- 
trymen and  partly  held  the  same  opinion  as  the  Germans. 
The  contrast  now  assumes  this  aspect:  Improvement  may 
be  obtained  by  selecting  single  excellent  individuals,  and 
experience  teaches  that  they  will  yield  a  constant  and  uniform 
progeny.     This  is  the  old  EngUsh  principle,  by  means  of 


66  PLANT-BREEDING 

which  new  races  are  not  created  but  simply  isolated  from 
among  a  mixture.  The  alternative  principle  is,  that  a  race 
may  be  improved  and  educated  in  arbitrarily  chosen  direc- 
tions. The  original  race  is  thereby  assumed  to  be  pure 
and  uniform,  and  thus  there  is  no  reason  for  beginning  with 
one  single  indi\idual.  It  is  even  better  to  start  from  a 
handful  of  ears,  and  to  select  in  each  generation  a  similar 
numljcr,  in  order  to  be  sure  that  all  characters  which  are 
not  consciously  considered  in  the  selection  may  remain  in 
the  average  condition  which  they  held  in  the  original  variety. 
Concerning  the  causes  of  the  improvement  in  this  re- 
peated selection,  two  contrasting  views  have  been  discussed. 
Hallett  assumed  that  variabiUty  was  induced  or  at  least  in- 
creased in  the  desired  direction  by  his  treatment.  In  Ger- 
many the  opposite  view  was  held,  and  it  was  even  assumed 
that  all  changes  induced  by  outer  influences  had  no  hered- 
itary power  at  all.  They  were  considered  as  delusive,  and 
the  principle  followed  was  to  exclude  them  carefully.  In- 
ternal causes  were  the  real  source  of  variabihty,  and  these 
had  to  be  guided  by  selection.  And  since  those  internal 
causes,  from  their  very  nature,  were  not  accessible  to  man, 
selection  was  considered  the  only  real  means  of  improvement. 
It  worked  slowly  and  often  did  not  work  at  all,  Ijut  wherever 
a  success  was  obtained,  it  was  ascribed  to  the  influence  of 
this  selection. 

■  As  I  have  already  stated,  methodical  selection  was  as- 
sumed to  produce  races  which  could  only  be  kept  up  to  their 
high  standard  by  a  continuation  of  the  selection.  This 
point  was  of  the  highest  practical  interest  for  the  breeder, 
since  it  kept  the  production  of  the  seed-grains  of  his  race  in 
his  own  hands,  at  least  for  a  long  succession  of  years,  and 
thereby  enabled  him  to  secure  very  considerable  profits. 
On  this  account  it  is  onlv  natural  that  many  breeders  of  cere- 
als of  the  present  time  still  adhere  to  these  old  convictions. 


V 


NILSSON'S   DISCOVERY  67 

As  an  instance,  1  may  cite  the  station  for  breeding  cereals 
and  potatoes  at  Nassenheide  near  Stettin  in  Germany, 
which  is  under  the  direction  of  Comit  x\rnim  Schlagentliin. 
Althougli  in  the  main  it  offers  for  sale  the  new  races  produced 
at  Svalof  hx  the  methods  to  be  described  in  our  next  chapter, 
it  recommends  the  sale  of  the  grains  on  the  basis  of  the  old 
views  of  dependency  on  elite  strains  instead  of  simply  laying 
stress  upon  the  purity  of  its  products. 

Finally,  a  question  is  to  be  considered  which  has  more  of  j 

scientific  than  of  practical  interest.  Though  the  isolation  of 
iadi  vidua  Is  of  exceptional  excellence  and  the  methodical 
improvement  of  races  are  absolutely  contrasting  principles, 
it  is  evident  that  they  do  not,  in  reahty,  need  to  exclude  one 
another.  Quite  on  the  contrary,  it  might  be  conceded  that 
isolation  is  one  process,  but  that  the  isolated  types  them- 
selves can  afterwards  be  improved  by  selection.  Tliis  con- 
ception would  lessen  the  difference  between  the  opposite 
views  and  at  the  same  time  make  them  comply,  at  least 
apparently,  with  the  idea  of  an  origin  of  species  in  nature 
by  means  of  slow  and  gradual  changes.  Theoretically,  no 
objection  could  be  made  to  this  proposition  and  it  would  only 
remain  to  test  its  value  by  direct  experiments.  Practically, 
however,  the  proposition  would  be  a  purely  hypothetical  one, 
instead  of  being  derived  from  the  experience  of  the  breeders, 
and  it  is  manifest  that  these  would  thereby  as  well  lose 
their  significance  as  a  support  for  Wallace's  views  on  the  ^ 
origin  of  wild  species. 

C.       THI<:    SVALOF     METHOD     OF     PRODUCING     IMPROVED 

RACES. 

The  criticism  of  the  reliability  of  the  German  method  of 
race-amelioration  was  part  of  the  work  during  the  first  period 
of  the  operation  of  the  experiment  station  at  Svalof.  It  had 
not  yet  been  conducted  to  a  definite  conclusion,  when,  in 


><C 


68  PLANT-BREEDING 

the  year  1890,  the  present  Director,  Dr.  Hjalmar  Nilsson 
was  appointed  as  such.  With  a  broad  conception  of  the 
practical  interests  of  Swedish  agriculture,  he  combined  the 
conviction  that  only  really  scientific  studies  are  adec[uate  to 
the  solution  of  difficult  practical  problems.  A  thorough 
knowledge  of  the  laws  of  variability  and  inheritance  seemed 
to  him  to  be  the  principal  requirement  for  the  solution  of 
the  prevailing  problems.  As  we  shall  presently  see,  it  has 
afforded  him  the  answer  to  the  main  questions  and  after- 
ward led  him  to  the  establishment  of  his  great  principle  of 
correlated  variabihty  as  one  of  the  principal  foundations  of 
agricultural  plant-breeding.  But  the  interest  of  this  sub- 
ject is  great  enough  to  justify  a  separate  treatment,  and  so 
we  shall  at  present  defer  it  to  another  occasion. 

Before  going  into  details,  I  will  give  a  short  survey  of 
the  work,  in  order  to  facihtate  its  appreciation.  Progress 
has  chiefly  been  achieved  by  the  discovery  of  the  numerous 
elementary  units  of  which  the  ordinary  varieties  of  cereals  are 
built  up.  That  varieties  were,  as  a  rule,  neither  pure  nor 
uniform,  was  a  fact  that  could  no  longer  escape  observation, 
and  selection  as  a  means  of  purifying  the  races  and  of  keep- 
ing them  up  to  their  main  standard  had  already  received 
general  recognition.  But  no  agriculturist  had  even  the  re- 
motest idea  of  the  real  state  of  their  compound  nature,  and 
not  even  the  work  of  Le  Couteur  and  ShirrefT  had  been 
sufficient  to  afford  such  a  conception.  A  protean  group  of 
types  was  found  to  constitute  each  so-called  variety.  These 
types  were  seen  to  be  different  from  one  another  in  a  pre- 
viously unsuspected  degree,  covering  a  range  of  variability 
adequate  to  comply  with  almost  all  the  needs  of  practice. 
Moreover,  these  types  proved  to  be  constant;  they  had  only 
to  be  isolated  and  multiplied  to  yield  new  and  uniform  races, 
directly  suitable  for  the  farmers'  purposes. 

Confronted  with  these  new  facts,  the  current  conception 


Fig.  19.     Svalof  Concordia  pea,  a  most  productive 
erect  new  variety  of  green  jieas,  produced  at  Svalof. 
69 


70  PLANT-BREEDING 

of  variability  itself  had  to  be  reconsidered.  It  is  rather  a 
state  of  ])c)lym()rphy.  The  idea  of  continual  changes  can 
hardly  be  connected  with  it.  It  is  the  existence  of  numer- 
ous different  forms,  each  of  which  is  simple  and  almost  in- 
variable. The  term  should  convey  the  idea  of  a  mixture, 
but  hardly  refers  to  actual  changes  in  the  constituent  types. 
Xilsson  began  his  work  l:)y  selecting  a  considerable  num- 
ber of  sam])les  from  the  varieties  on  the  fields  of  the  station, 
but  in  doing  so,  he  still  followed  the  prevailing  method. 
Each  sample  was  sown  on  a  separate  field  plot  and  progress 
was  tested  in  regard  to  ])urity  and  quality.  Nearly  a  thou- 
sand lots  were  cultivated,  but  the  result  was  as  unsatisfactory 
as  before.  Everywhere  the  groups  were  seen  to  be  hetero- 
geneous and  to  consist  of  a  more  or  less  motley  mixture  of 
types.  The  samples,  howe\'er,  had  been  chosen  under  the 
assumption  that  they  were  uniform,  and  it  h;id  been  expect- 
ed that  they  would  yield  each  a  uniform  progeny.  This 
however,  was  not  the  case,  and  doubts  arose  as  to  the  re- 
liability of  the  whole  process  of  selection.  If  the  progeny 
does  not  correspond  to  the  mother  plants  from  which  it  is 
derived,  how  can  we  tell  that  the  next  selection  will  produce 
a  generation  with  the  desired  qualities? 

_A11  reliability  of  the  selection-principle  seemed  to  dis- 
appear, when,  fortunately,  an  accidental  observation  was 
made  which  at  once  changed  the  whole  aspect  of  the  ques- 
tion. Some  few  cultures  were  discovered  among  the  thou- 
sands which  bore  only  one  type.  They  wx-re  as  uniform  as 
the  remainder  were  heterogeneous.  Concerning  the  initial 
choice  of  the  samples,  an  elaborate  record  had  been  kept, 
and  tliis  enabled  Nilsson  to  discover  the  cause  of  the  purity 
of  these  exceptional  cases.  According  to  the  accepted 
method,  each  sample  had  consisted  of  a  certain  number  of 
ears,  which  were  as  similar  to  one  another  as  could  be  ex- 
pected, and  which  were  therefore,  simply  taken  to  belong 


NILSSON'S   DISCOVERY  71 

to  the  same  type.  But,  of  course,  the  number  of  ears  had 
been  different  in  the  different  groups,  some  being  common 
and  represented  by  numerous  indivichials  and  others  being 
rare.  Among  the  rarest,  some  types  had  only  been  met 
with  in  one  single  head,  and  since  the  number  of  the  ears 
had  been  entered  for  each,  it  could  be  made  out  at  the  time 
of  the  testing  of  the  cultures,  which  among  them  were  in 
this  exceptional  condition. 

To  this  accidental  circumstance,  combined  with  the  ex- 
act scientific  method  of  keeping  extensive  records,  the  dis- 
covery of  the  cause  of  the  diversity  of  the  cultures  was  due. 
For  precisely  those  cultures  which  were  derived  from  one 
ear  only  were  found  to  be  pure  and  uniform,  all  others 
offering  to  the  eye  a  more  or  less  motley  assemblage  of  forms. 
Hence  the  conclusion  that  cultures,  in  order  to  be  pure, 
must  be  started  from  single  ears.  Two  or  more  ears  may 
seem  similar  enough  to  be  considered  as  representatives  of 
the  same  type,  while  in  reality  they  do  not  afford  suffi- 
ciently reliable  marks. 

On  the  basis  of  this  discovery,  a  distinction  had  to  be 
made  between  the  selection  of  samples  and  the  selection  of 
individual  ears  or  panicles.  The  older  experiments  had 
always  been  started  from  multiple  samples,  according  to  the 
prevaihng  views,  and  it  became  at  once  clear  that  at  least 
one  cause  of  their  usual  miscarrying  must  be  sought  in  this 
course  of  procedure.  They  must  be  designated  as  selections 
of  groups  or  of  families,  and  could  even  appropriately  be 
denominated  selections  of  crowds,  an  expression  which  would 
at  once  convey  the  idea  that  the  terms  of  selecting  simulta- 
neously more  than  one  individual  are  intrinsically  contra- 
dictory. 

Contrasting  with  this  old  principle,  the  new  one  was 
designated  as  that  of  the  separate  selection  or  separate  cul- 
tures.    It  has  also  received  the  name  of  pedigree- cultures, 


72  PLANT-BREEDING 

but  with  another  significance  to  the  word  than  that  used  by 
Hallett,  as  we  shall  soon  see.  It  opened  the  prospect  of  a 
new  manner  of  operating  and  that  at  a  time  when  the  results 
of  the  previous  methods  had  become  such  as  to  make  all 
further  trials  almost  hopeless.  ' 

As  yet  it  was,  however,  only  a  presumption,  resting  on 
the  small  evidence  quoted.  It  was  more  an  indication  of 
what  could  be  expected  than  a  proof  of  what  really  was. 
It  had  first  to  be  tested.  This  was  done  at  once,  and  on  as 
large  a  scale  as  possible.  It  was  in  the  summer  of  1892 
that  the  described  rare  uniform  plots  were  seen,  and  in  the 
harvest  of  the  same  year  a  renewed  search  for  starting-points 
for  new  races  was  made.  But  this  time  each  ear  was  kept 
separate,  <jnd  two  or  more  heads  were  combined  only  when 
they  were  gathered  on  the  same  individual  plant.  Some 
^ai^~were  chosen  as  the  best  representatives  of  their  varie- 
ties, others  as  deviating  from  the  type  in  one  respect  or 
another.  All  in  all,  about  two  thousand  ears  and  panicles 
of  different  species  and  varieties,  representing  as  many 
divergent  types  as  possible  were  selected.  The  grains  of 
each  were  sown  on  a  separate  plot,  and  next  year  all  the 
groups  were  descended  from  one  single  mother  plant  each. 

The  results  of  this  trial  greatly  exceeded  all  previous 
expectations.  Almost  all  the  numbers  were  seen  to  be  uni- 
form, all  the  offspring  of  a  single  plant  being  wholly  similar.- 
Exceptions  there  were,  but  they  were  exceedingly  rare.  For 
instance,  among  the  422  cultures  of  oats,  397  were  uniform 
and  only  25  multiple.  But  of  course  it  could  be  expected 
that  among  so  large  a  number  of  ears,  some  hybrids  would 
be  met  with,  and  others  which  would  be  only  partially  self- 
fertiUzed,  but  for  the  remaining  part  contaminated  by  the 
pollen  of  their  neighbors.  In  either  case,  the  progeny 
would  be  dissimilar,  and  especially  in  the  former  the  splitting 
up  of  the  hybrids  would  give  rise  to  quite  a  considerable 


NILSSON'S  DISCOVERY  73 

degree  of  dissimilarity.  The  cases  of  such  mixed  progeny 
were  rare  enough  to  be  considered  as  the  consequence  of 
the  selection  of  such  hybrids,  and  special  experiments  have 
since  given  sufficient  proof  of  the  truth  of  this  assertion. 
Leaving  these  hybrids  aside,  the  cultures  of  1893  advanced 
the  importance  of  the  selection  of  single  individuals  as  the 
one  reliable  source  of  purity,  to  the  rank  of  an  experimentally 
established  fact. 

From  this  fact  it  could  further  be  deduced  that  a  repeated 
selection  would  be  unnecessary.  The  next  generation 
might  be  expected  to  be  as  pure  and  as  true  to  the  type  as 
the  first.  Moreover,  the  uniformity  was  such  as  to  make 
another  selection  simply  impossible.  All  the  differences 
which  formerly  afforded  the  material  for  selection  had  dis- 
appeared from  these  new  strains.  They  were  observed  to 
exist  among  the  separate  cultures,  and  allowed  a  compari- 
son of  these  in  exactly  the  same  sense  as  they  formerly  had 
made  possible  a  choice  in  the  fields.  But  within  each  cul- 
ture no  other  differences  were  seen  than  those  unavoidable 
degrees  in  development  which  result  from  the  differences 
in  location  between  the  central  plants  and  those  of  the  border, 
or  between  accidentally  crowded  or  locally  favored  individ- 
uals, and  the  average  of  the  group. 

These  observations  led  to  the  establishment  of  the  second 
great  principle,  that  of  the  sufilciency  of  the  one  initial 
choice.  After  that,  the  newly  isolated  type  has  only  to  be 
multiplied  and  to  be  kept  free  from  accidental  admixtures. 
On  this  point,  the  Svalof  method  agrees  with  the  principles 
observed  by  Te  Couteur  and  Shirreff,  who,  Hkewise,  did  not 
repeat  their  selection.  For  the  industrial  side  of  the  work, 
this  principle  has  a  high  value.  In  the  beginning,  it  was 
feared  that  the  reduction  of  the  commencement  of  a  race  to 
one  single  head  might  protract  its  multiplication  so  as  to  re- 
quire more  generations  to  reach  the  quantity  necessary  for 


Fig.  20.     Svalof  Pearl  summer  wheat,   not  layering,  early  ripening,  with 
full  rounded  kernels,  that  keep  in  the  cars  at  harvest  time. 


74 


Fig.  21.     Ordinary  Butt  summer  wheat,  for  comparison  with  the  improved 
variety  of  the  previous  figure. 


75 


76  PLANT-BREEDING 

its  ultimate  distribution.  Experience,  however,  soon  showed 
this  fear  to  be  unfounded,  since  the  elimination  of  all  further 
selection  soon  overcomes  the  incipient  deficiency.     In  reality, 


Figs.  22-26.    Five  different  types  of  new  varieties  of  oats,  produced  at  .Svalof. 
Fig.  22.     Flag-oats. 

the  multiplication  of  a  sejiarate  culture  may  go  on  as  fast 
or  even  faster,  than  that  of  an  old-fashioned  methodical 
selection. 

In  the  fall  of  1893,  these  new  principles  could  be  consid- 


NILSSON'S   DISCOVERY  77 

ered  as  wholly  established.  At  once  they  were  raised  to 
the  rank  of  an  exclusive  method.  Of  course,  the  existing 
cultures  could  not  easily  be  given  up,  but  they  could  be 
rapidly  diminished.  After  three  years,  almost  all  the  exper- 
iments were  of  the  separate-culture  sort,  and  of  older  va- 
rieties only  a  small  number  were  kept,  and  destined  to  afford 
the  material  for  a  comparison  of  the  novelties  with  the  types 
they  were  called  upon  to  replace.  Since  that  time,  the  se- 
lection of  crowds,  or  even  of  small  groups  of  heads,  has  com- 
pletely been  abandoned  at  Svalof,  and  all  the  numerous  new 
sorts  which  the  station  has  since  introduced  into  the  trade 
are  derived  each  from  a  single  individual.  Consequently, 
they  are  absolutely  pure,  and  purity  is  for  them  such  a  matter 
of  course  that  often  it  is  hardly  mentioned  at  all. 

Pure  races,  however,  are  by  no  means  the  sole,  or  even 
the  first,  requisite  of  the  farmer.  Al)ove  all,  they  must  have 
better  quahties  and  yield  a  richer  harvest  than  the  ordinary 
varieties.  Thus  the  question  arose  whether  the  separate- 
cultures  would  satisfy  in  this  respect.  But  even  here  they 
were  found  to  surpass  all  expectations.  Of  course,  of  two 
thousand  types,  all  cannot  be  excellent.  But  manifestly 
this  is  not  at  all  necessary.  It  is  cjuite  sufficient,  if  among 
them,  some  few  are  found  having  really  excellent  equalities. 
A  careful  comparison  of  the  families  of  the  year  1893 
showed  that  their  mutual  differences  were  much  greater 
than  could  be  surmised  from  the  amount  of  variability  ob- 
served in  the  fields  at  the  time  of  selection.  IMoreover,  the 
separate-cultures  complied  with  the  most  cUverse  require- 
ments, some  being  highly  resistant  to  frost,  others  to  dis- 
eases, some  being  suited  for  hard  and  others  for  light  soils, 
some  being  early  and  others  late  in  ripening,  some  surpass- 
ing others  by  the  stiffness  of  their  culms,  the  length  of  their 
ears,  the  number  and  size  of  their  grains,  and  so  on.  Hard- 
ly any  demand  could  be  pointed  out,  with  which  at  least 


78  PLANT-BREEDING 

one  of  the  new  varieties  did  not  comply.  The  experimental 
fields  were  in  some  sense  large  exhibits  on  which  each  farmer 
could  seek  out  the  types  that  would  best  suit  his  soil  and  his 
local  conditions. 

This  choice,  however,  had  to  be  made  at  the  station  it- 
self. It  was  impossible  to  multiply  even  many  hundreds  of 
the  new  sorts.  The  l)est  had  to  be  chosen,  and  in  order  to 
do  this,  all  of  them  had  to  be  compared  with  tlie  utmost 
care.  A  second  line  of  work  had  to  be  set  up,  as  important 
as  the  hrst,  but  requiring  a  far  larger  amount  of  labor.  The 
new  varieties  had  to  be  studied  and  tested,  and  to  be  tried 
from  all  points  of  view.  The  stud)'  had  to  emljrace  their 
whole  lifetime,  and  the  botanical  marks  and  biological 
symptoms  as  well  as  the  industrial  f|uaHties,  and  their  re- 
([uirements  with  respect  to  treatment.  The  botanical  and 
biological  characters  of  the  new  sorts  came  first,  because 
they  were  more  easily  stucUed  and  because  they  afforded 
an  opportunit}'  of  reducing  the  number  of  the  strains  con- 
siderably without  the  time-consuming  and  expensive  tests 
of  the  industrial  c|ualities.  In  the  meantime,  all  the  families 
were  multiphed  as  fast  as  possible.  As  soon  as  some  fell 
out,  the  space  left  free  was  occupied  by  the  remaining  strains. 
In  this  way,  nearly  the  same  extent  of  the  field  v.-as  sufficient 
for  the  whole  group,  during  a  series  of  years.  In  the  end, 
only  a  few  remained,  but  these  had  been  tested  in  all 
directions  and  found  to  be  the  very  best.  Of  course,  thev 
had  also  been  compared  with  the  ordinary  unselectcd  va- 
rieties, and  Ijeen  proven  to  far  surpass  these.  Five  or  six 
years  of  continuous  testing  and  of  corresponding  multipli- 
cation are  usually  required  before  the  end  is  reached.  It  is 
(juite  sufficient  when  some  few  new  varieties  are  yearly  added 
to  the  stock.  So  in  the  year  igoi,  eighteen  excellent  new 
types  were  offered  to  the  trade.  Among  them,  were  five 
new  kinds  of  wheat,  six  of  barlev,  three  of  oats  and  four  of 


NILSSON'S   DISCOVERY  79 

vetches.  Each  new  kind,  of  course,  is  given  a  separate 
name  which  partly  incUcates  its  quahty  and  partly  its  origin. 
As  instances  I  may  give  the  Svalof  Grenadier  wheat,  the 
Svalof  Swan-necked  barley,  the  Svalof  Great  Mogol  black 
oats  and  others.  From  the  details  given,  it  may  easily  be 
gathered  that  the  multiplication  and  comparative  study  of 
the  isolated  races  eml)races  the  largest  part  of  the  work  per- 
formed at  Svalof.  Besides  this,  tlie  initial  choice  and  the 
starting  of  the  new  varieties  is  only  a  matter  of  temporary 
concern.  The  comparative  studies  reciuire  the  trials  of 
many  hundreds  of  pedigree-cultures,  and  accorcUngly  an 
accurate  system  of  book-keeping  is  one  of  the  essential  feat- 
ures of  the  work.  From  its  first  isolation  each  culture  is 
designated  Ijy  a  number,  which  it  retains  until  it  is  aban- 
doned or  until  it  is  judged  worthy  of  introduction  into  com- 
merce. Then,  of  course,  the  number  is  replaced  by  an 
ordinary  name,  as  quoted  above.  The  book  numbers  at 
Svalof  consist  of  four  figures,  the  first  of  which  is  a  zero, 
which  is  prefixed  to  avoid  all  confusion  with  other  numbers. 
The  second  figure  indicates  the  group  and  the  two  remaining 
ones  relate  to  the  special  sort.  So  a  dwarf  Ligowo  oats  is 
called  0313,  and  another  kind  of  Ligowo  oats  which  was 
afterward  recommended-  as  Svalof  Ligowo,  bore  the  number 

of  03S3- 

The  amount  of  this  book-keeping  is  almost  incredible. 
In  the  year  1900,  some  2600  numbers  were  in  culture,  partly 
relating  to  different  grains,  including  corn,  and  partly  to 
leguminous  plants,  such  as  peas,  beans  and  vetches.  To 
these  numbers  must  be  added  138  comparative  cultures  of 
races  almost  ready  for  introduction  into  the  trade,  and 
among  these  only  twelve  older  ones  were  found,  the  remain- 
ing 126  having  all  been  isolated  by  the  new  Svalof  method. 
Further,  the  book-keeping  was  increased  in  the  same  year 
by  431  numbers  afforded   by  the  progeny  of  mother  plants 


8o  PLANT-BREEDING 

which  had  been  selected  anew  in  the  fields  during  the  pre- 
ceding season.  The  book-keeping  embraces  the  complete 
botanical  description  of  each  new  sort,  from  its  germination 
until  the  time  of  the  harvest,  with  all  the  details  required 
for  the  controlling  of  its  constancy  and  uniformity,  and  for 
the  study  of  all  those  quahties  upon  which  the  hitroduction 
into  general  agriculture  will  ultimately  depend. 

I  have  purposely  left  the  hybrids  out  of  consideration 
until  this  time.  In  the  beginning  we  saw  that,  although  uni- 
formity is  the  prevailing  rule  for  the  progeny  of  a  single 
mother  ])lant,  exceptions  regularly  occur.  These  have  been 
ascribed  to  the  effect  of  accidental  crosses.  Until  some  time 
ago  it  was  assumed  that  crosses  were  of  common  occurrence 
only  with  rye,  the  other  grains  fertilizing  themselves.  But 
experience  has  shown  that  this  is  only  an  average  rule,  and 
that  everywhere  in  the  fields  accidental  crosses  may  occur. 
Their  progeny  are,  of  course,  hybrids,  and  these  may  split 
in  the  next  generation  according  to  distinct  laws,  as  studied 
for  cereals  by  Rimpau  and  other  investigators.  Any  char- 
acter which  was  different  in  the  two  parents  of  the  cross, 
may  thus  split  in  the  progeny  of  the  hybrid,  and  in  this 
way  new  combinations  of  characters  may  arise.  Experience, 
however,  shows  that  in  ordinary  fields  almost  all  possible 
combinations  may  be  met  with,  and  it  is  to  be  presumed 
that  at  least  the  greater  number  of  them  are  due  to  crosses 
in  previous  and,  perhaps,  in  long- forgotten  years.  In  the 
following  generations,  these  new  combinations  of  character 
may  become  fixed  in  part  of  the  progeny  of  the  hybrids,  and 
it  is  a  well-known  fact  that  such  constant  races  are  the  ordi- 
nary results  of  natural  and  artificial  crosses.  Hence,  we  may 
conclude  that  some,  and  perhaps  many,  of  the  types  which 
may  be  selected  and  isolated  in  the  fields  and  which  prove 
to  be  constant  races  must  be  of  hybrid  origin. 

Whenever  such  an  original  hvbrid  is  found  in  the  field 


NILSSON'S   DISCOVERY  81 

and  selected  for  some  peculiar  quality,  it  will  repeat  the  same 
splittings  in  its  progeny  and  thus  be  found  not  to  give  rise 
to  a  pure  and  uniform  race.  This,  however,  is  no  drawback. 
On  the  contrary,  it  often  affords  a  means  of  acquiring  new 
and  useful  varieties.  The  selection  has  only  to  be  repeated, 
the  hybrid  group  being  treated  in  the  same  way  as  the 
cultures  of  the  original  fields.  For  each  type  one  ear  must 
be  selected,  and  its  kernels  must  be  sown  separately.  Accord- 
ing to  the  ordinary  rules  of  hybrids,  some  of  these  separate  cul- 
tures will  at  once  prove  uniform,  but  others  will  repeat  their 
sphttings.  x\mong  these,  the  choice  must  be  repeated  once 
more,  and  by  continuing  this  process  we  may  finally  succeed 
in  getting  all  the  possible  combinations  in  constant  and  uni- 
form races.  These,  though  of  hybrid  origin,  have  definitely 
lost  the  character  of  variabihty,  which  at  the  beginning  dis- 
tinguished the  progeny  of  the  original  cross.  They  are 
further  cultivated  and  tested  in  exactly  the  same  way  as  all 
other  separate  cultures,  and  may  yield  as  valuable  agricul- 
tural varieties  as  these. 

The  work  of  Svalof  is  not  connected  with  the  origin  of 
the  elementary  species  which  are  observed  in  the  field. 
This  is  a  question  of  purely  scientific  interest.  Two  possibil- 
ities offer  themselves.  Either  the  high  degree  of  variabihty 
is  old  and  the  same  elementary  types  which  are  now  existing 
have  already  existed  for  centuries,  or  the  production  of  new 
varieties  is  steadily  going  on,  afforchng  a  cause  of  increasing 
variabihty  or,  at  least,  of  a  changing  group  of  units.  In  the 
first  case  the  mixtures  would  be  constant  and  only  exposed 
to  accidental  losses  by  the  crowding  out  of  some  of  their 
rarer  constituents.  In  the  latter  case,  however,  the  process 
must  be  assumed  to  be  a  slow  one,  and  the  existence  of 
hundreds  of  types  is  no  proof  of  a  high  degree  of  change- 
ability. This  conclusion  will  easily  be  arrived  at  from  the 
following  considerations.     The  ever-occurring  crosses  must 


82 


PLANT-BREEDING 


have  the  effect  of  rupidh*  increasing  the  number  of  types, 
even  if  ordinary  mutal)ility  is  slow  in  prockicing  new  units. 
For,  by  this  crossing,  each  new  unit  will  become  united 


Fig.  23.     Stiff-branched  Svalof  oats. 

with  many  of  the  existing  types  and,  in  the  end,  perhaps, 
with  all  of  them.  In  this  way,  the  production  of  one  really 
new  unit  will  tend  to  double  the  number  of  the  existing 
types,  and,  in  tlie  cases  of  many  ,L':ardeii  llowers,  where  such 


NILSSON'S   DISCOVERY 


83 


crosses  have  been  artificially  made,  the  fact  that  one  new 
character  by  this  means  yields  a  very  large  number  of  new 
varieties  is  universallv  known,  and  one  of  the  most  ordin- 


Fig.  24.     Svalof  oats  with  spreading  branches. 

arv  means  of  producing  novelties.  Tvloreover,  if  one  new 
unit  may  double  the  number  of  the  separate  types,  a  second 
new  unit  may  tend  t()  increase  it  fourfold,  a  third  eightfold, 
and  so  on.     From  this  calculation  it  mav  l)e  seen  that  even 


84  PLANT-BREEDING 

a  thous'ind  separate  types  of  coml:»inations  do  not  require 
more  than  ten  mutually  independent  changes.  Or,  in  other 
words,  the  wide  range  or  \-ariability  observed  on  grain  liclds 
may  be  the  effect  of  the  production  of  a  few  novelties,  com- 
bined with  a  sufficient  degree  of  intercrossing.  Hence,  it 
follows  that  one  real  change  of  some  character  in  a  year,  or 
even  in  ten  or  more  years,  must  be  considered  as  wholly  suf- 
ficient for  an  explanation  of  the  observed  variability.  If  we 
take  it  that  these  changes  ai)pear  suddenly,  or  in  other  words, 
are  mutations,  then  an  ordinary  degree  of  mutability,  such 
as  is  ([uite  common  with  horticultural  plants,  seems  to  be 
all  that  is  re([uired  to  explain  the  numerous  types  observed 
at  Svalof.  The  niiin  difference  would  be  that  in  liorticul- 
turc  all  profitable  varieties  have  been  observed  and  isolated 
as  soon  as  they  have  appeared,  but  that  in  agriculture  they 
have  been  allowed  to  pass  without  observation,  or  at  least, 
without  appreciation.  Consecjuently,  the  larger  horticul- 
tural groups,  such  as  asters,  carnations  and  dahlias,  now 
contain  hundreds  of  well-defined,  pure  and  uniform  varieties, 
but  the  agricultural  varieties  are  still  almost  everywhere 
mixtures  awaiting  the  process  of  sifting  and  testing. 

The  experiments  of  Svalof,  however,  give  at  least  some 
evidence  concerning  the  probable  origin  of  the  variability  of 
the  cereals.  Up  to  tliis  time  I  have  described  the  pedigree- 
cultures  as  constant  and  uniform,  and  only  excluded  the  case 
of  the  hybrids.  But  even  within  the  purest  races  deviations 
may  occur  from  time  to  time,  though  rarely,  and  these  may 
be  compared  with  what  probably  happens  in  the  field.  When 
a  race  is  started  from  one  selected  mother  plant  and  multi- 
plied during  some  years  so  as  to  cover  hundreds  of  acres,  it  is 
ordinarily  seen  to  keep  wholly  pure,  all  the  thousands  of  in- 
dividuals displaying  the  same  characters  and  qualities.  This 
is  precisely  the  special  feature  and  the  advantage  of  the  cul- 
tures after  the  Svalof  principle.     But,  from  time  to  time,  one 


NILSSON'S   DISCOVERY  85 

single  specimen  among  the  hundreds  of  thousands  will  sport, 
deviating  in  some  mark  from  the  main  type.  As  soon  as  such 
an  event  is  noticed,  the  sporting  individual  h  usually  isolated 
and  its  grains  are  saved  separately. 

This  is  practically  nothing  more  than  a  new  initial  selec- 
tion, a  starting-point  for  a  new  race,  which  has  to  be  isolated, 
multiplied  and  tested  in  the  same  way  as  all  the  others,  and 
has  at  least  an  equal  chance  with  them  of  yielding  a  valuable 
contribution  to  agricultural  practice.  Some  very  good 
novelties  have  been  obtained  in  this  way  at  Svalof.  These 
changes  come  on  unexpectedly  and  all  of  a  sudden,  exactly  as 
ordinary  mutations.  No  visible  preparations  and  no  groups 
of  intermediate  forms  accompany  them.  They  are  at  once 
quite  distinct  from  the  main  type.  But,  like  mutations,  they 
may  be  confused  with  the  effects  of  accidental  crosses,  and 
such,  though  very  rare,  are  also  seen  to  occur  in  the  experi- 
mental fields  of  pedigree-races  at  Svalof.  Crosses  may  yield 
hybrids  which  will  split  in  succeeding  generations  as  we  have 
seen,,  and  whenever  the  result  of  the  isolation  and  separate 
multiplication  of  a  sporting  individual  is  a  heterogeneous 
group,  it  must  be  assumed  that  the  deviation  was  due  to  a 
cross. 

On  the  other  hand,  such  a  cross  does  not  necessarily 
exclude  a  real  mutation,  since  mutations  are  believed  to  occur 
in  the  production  of  sexual  cells  and  so  may  be  limited  either 
to  the  pollen  or  to  the  ovaries  of  a  mutating  plant.  But  this 
theoretical  side  of  the  question  does  not,  strictly  speaking, 
belong  to  our  present  discussion,  and  so  it  may  be  considered 
sufficient  to  have  indicated  it.  My  only  aim  was  to  point  out 
the  difficulties  which  here,  as  everywhere,  are  found  in  the 
way  of  distinguishing  between  mutants  and  accidental  hy- 
brids. This,  however,  has  reference  only  to  the  special  cases, 
but  from  a  broad  point  of  view  the  experimenters  of  the 
staff  of  Svalof  are  satisfied  that  real  mutations  as  well  as 


86 


PLANT-BREEDING 


accidental  crosses  arc  occurring  in  their  pure  pedigree-cul- 
tures, from  time  to  time. 

Some  instances  may  be  given.     Among  the  cultures  of 


Fi^.  2;      Svalof  oats  with  bending  branches. 


pedigree  wheat  started  from  an  initial  selection  made  in  the 
year  1892,  a  race  indicated  by  the  book  number  0608  distin- 
guished itself  by  long  and  stiff  culms,  combined  with  an  un- 
usually good  quality  of  the  grains.     But  it  had  two  notable 


NILSSON'S    DISCOVERY  87 

defects,  hairy  scales  and  lonsj;  awns.  On  account  of  these 
dclicicncics,  it  was  considered  improbable  that  it  could  ever 
be  introduced  into  practice.     During  four  years  the  race  kept 


Fig.  26.     Svalof  oats  with  weak  branches. 

pure  and  true  to  its  characters,  but  in  the  year  1896  one  single 
jjlant  distinguished  itseh  by  the  lack  of  awns  and  by  a  some- 
what deviating  size  and  shape  of  the  cars.  Its  grains  were 
saved  scparateh-  and  produced  a  ^•ery  heterogeneous  mixture 


88  PLANT-BREEDING 

of  types,  among  which  some  showed  a  new  quality  in  that 
their  scales  were  smooth.  Smooth  and  hairy  scales  occur- 
red both  on  ears  with  and  without  awns,  thus  constituting 
four  principal  types  in  which  the  remaining  differentiating 
marks  gave  races  of  an  inferior  rank.  The  next  generation 
still  showed  some  splitting  but  soon  the  isolated  types  became 
constant  and  uniform,  eight  of  them  being  distinct  enough 
to  justify  a  more  comprehensive  testing.  Those  which  lacked 
the  hairiness  and  the  awns  were,  of  course,  considered  as 
distinct  improvements,  and  as  such  received  new  numbers 
in  the  pedigree-book.  Besides  these  two  quaUties,  they  also 
had  denser  ears  of  better  construction  and  stiffer  culms,  while 
in  other  respects  they  had  kept  the  excellent  characters  of  the 
parent  form.  Soon  afterward  the  cold  winter  of  igoo-oi 
showed  them  to  possess  an  exceptional  degree  of  resistance  to 
frost,  and  thereby  elevated  them  to  the  first  rank  among  all 
the  novelties  of  winter  wheats.  In  concluding  the  descrip- 
tion of  this  most  interesting  case  of  variation  it  remains  to 
be  stated  that  the  parent-strain  from  which  it  sprang  has  since 
remained  as  j)ure  as  before,  never  repeating  the  novelty  nor 
producing  any  other. 

As  a  second  instance,  a  winter  variety  of  wheat  may  be 
chosen,  which  had  been  isolated  in  1892  from  the  Herren- 
hoflf- wheat  and  bore  the  number  0516.  It  is  distinguished 
by  long  and  narrow,  smooth  ears.  It  has  an  excellent  quahty 
of  grain  but  weak  culms,  and  moreover,  is  deficient  in  its  de- 
gree of  resistance  to  cold.  It  was  absolutely  pure  and  uni- 
form, but  produced  in  the  summer  of  1897  one  single  indi- 
vidual with  stiff  culms  and  short  and  rounded  ears.  The 
progenv  of  this  mutant  at  once  proved  constant  and  uniform 
and  quite  distinct  from  all  existing  varieties,  excelling  in  the 
marks  of  its  original  parent  as  well  as  by  \irtue  of  a  high  degree 
of  resistance  to  cold.  It  has  since  remained  absolutely  pure 
and  constant,  has  been  multipHed  during  five  years  and  given 


NILSSON'S   DISCOVERY  89 

to  the  trade  under  the  name  of  Zapfenweizen  or  egg-wheat, 
alluding  to  the  curious  egg-shape  of  its  heads.  The  parent 
form  wliich  produced  this  mutation  sported  twice  afterward, 
but  in  both  cases  its  products  were  multiple  in  the  beginning 
and  could  be  brought  to  uniformity  only  after  some  split- 
tings. 

Besides  wheat,  the  cultures  of  oats,  peas  and  vetches  are 
seen  to  produce  sports,  from  time  to  time,  at  Svalof.  Here, 
also,  the  sports  are  sudden  and  without  preparation  or  inter- 
mediates, each  of  them  at  once  constituting  a  new  type  which 
is  as  distinct  from  its  allies  as  any  new  form  found  in  the 
fields.  Not  rarely  these  changes  are  found  to  relate  to  the 
very  marks  on  account  of  which  the  parent  strain  had  origin- 
ally been  selected,  thus  constituting  a  distinct  progression 
of  mutabiUty  in  a  previously  determined  direction. 
Among  oats  one  of  the  most  prominent  novelties  of  Svalof 
has  originated  as  a  mutation  in  a  pedigree- culture  which  had 
remained  quite  uniform  during  the  8  or  10  preceding  years. 
It  is  one  of  the  best  black  kinds  and  has,  curiously  enough, 
been  produced  by  a  white  variety. 

In  contrast  with  wheat  and  oats,  the  barley  has,  until  now, 
remained  devoid  of  novelties.  Tliis  fact  is  very  important 
from  a  theoretical  point  of  view.  For  accidental  crosses  may 
be  produced  as  easily  in  barley  as  in  wheat  and  oats.  Direct 
extensive  experiments,  made  at  Svalof,  have  estabhshed  this 
fact  beyond  all  doubt.  Hence  we  may  conclude  that  on 
the  experimental  fields,  with  their  pure  pedigree-cultures, 
accidental  crosses  must  be  extraordinarily  rare,  even  when 
compared  with  the  rare  occurrences  in  ordinary  fields.  Evi- 
dently the  conclusion  must  hold  good  for  wheat  and  oats  as 
well  as  for  barley,  and  it  speaks  for  the  recognition  of  their 
sports  as  mutations  rather  than  as  crosses.  In  other  words, 
it  seems  probable  that  wheat  and  oats  are  still  in  a  mutative 
period,  Uke  so  many  of  our  garden  plants,  but  that  barley  is 


90  PLANT-BREEDING 

now  in  a  period  of  stability,  as  is  the  ease  with  the  larger 
number  of  our  wild  species. 

Summing  up  the  main  features  of  ^his  short  description 
of  the  method  of  selection  developed  by  Nilsson  and  his  sta.fi 
at  the  Swedish  agricultural  experiment  station,  we  may  point 
out  the  following  propositions:  Ordinary  varieties  of  cereals 
are  built  up  of  hundreds  of  elementary  forms  which,  with  few 
exceptions,  have  hitherto  escaped  observation.  They  may 
be  distinguished  in  the  fields  by  distinct  marks  derived  from 
their  botanical  characters,  and  will  afterward  prove  to  possess 
corresponding  differences  in  their  industrial  qualities.  They 
have  to  be  selected  but  once  and  afterward  will  be  ([uite  uni- 
form and  constant,  with  the  exception  of  accidental  hybrids 
which,  however,  will  also  yield  constant  and  pure  races  after 
repeated  selection.  The  purity  of  the  races  is  such  as  to  be 
practically  absolute,  but  this  does  not  exclude  the  occurrence 
of  stray  mutations  by  which  new  and  valuable  improvements 
ma}'  be  secured.  The  high  variability  which  is  commonly 
attributed  to  our  ordinary  varieties  of  cereals  consists  only  in 
the  differences  among  these  constituents  of  the  mixtures. 
But  these  differences  have  been  found  to  be  so  great  as  to 
afford  material  for  all  desirable  selections  and  to  yield  new 
races  for  all  the  cHmates  and  soils  of  Sweden,  for  all  the  di- 
vergent needs  and  demands  of  its  various  industries  and  even, 
to  a  large  extent,  for  exportation  into  other  countries. 

D.      A    CRITICISM    OF    THE    PRINCIPT.F,    OF    CONTINUOUS 
SELECTION. 

In  the  biological  sciences  the  name  of  Darwin  is  chiefly 
attached  to  two  great  principles,  the  theory  of  descent  and  the 
hypothesis  of  natural  selection. 

The  theory  of  descent  was  founded  by  Lamarck,  but 
it  owes  its  present  form  to  the  work  of  Darwin.  By  means 
of  immeasurable  groups  of  facts,  brought  together  from  the 


NILSSON'S    DISCOVERY  91 

various  results  of  systematic  research  and  of  niorphology,  of 
geography  and  paleontology,  he  not  only  contrived  to  con- 
vince the  biologists  of  his  time,  but  also  brought  the  principle 
of  evolution  to  almost  universal  acceptance.  Especially 
convincing  were  his  proofs  of  the  numerous  adaptations  of 
living  organisms  to  their  environments. 

The  principle  of  natural  selection  was  discovered  by  Dar- 
win himself.  In  a  general  way  he  showed  that  many  times 
more  individuals  are  born  than  can  possibly  survive.  Tliis 
results  in  a  struggle  for  life,  in  which,  apart  from  casualties, 
those  survive  which  are  the  best  litted  for  their  special  life- 
conditions.  By  this  struggle  the  weak  are  crowded  out,  and 
only  the  best- fitted  become  the  parents  of  the  subsequent 
generation.  Tliis  struggle  may  be  seen  at  work  at  every 
moment  and  on  every  field.  The  ehmination  of  the  weaker 
types  by  stronger  ones  also  has  often  been  observed.  But 
this  is  nearly  always  where  different  species  were  competing 
with  one  another.  Concerning  the  effects  of  the  intraspecific 
struggle  hardly  any  observed  facts  are  available.  \Miether 
it  takes  an  active  part  in  the  production  of  new  species,  and 
in  what  manner  it  may  be  able  to  do  so,  is  a  question  far 
beyond  our  present  obser\'ation. 

For  this  reason  Darwin  relied  for  a  large  part  on  the 
methods  of  selection  which  at  his  time  were  in  use  both  in 
agriculture  and  in  horticulture.  He  tried  to  show  that  the 
evolution  of  species  at  large  has  folloAved  the  same  laws  that 
underHe  the  evolution  of  races  and  varieties  in  culture.  In 
a  general  way  he  has  succeeded  in  con\'incing  his  contem- 
poraries of  the  validity  of  this  analogy.  Agricultural  and 
horticultural  experience,  however,  were  at  that  time  only  im- 
perfectly developed,  and  the  improvemicnt  of  races,  though 
successful  in  a  large  number  of  cases,  had  no  really  scientific 
foundation.  It  did  not  afford  all  the  evidence  required  by 
Darwin  for  a  thoroughly  reliable  theory.     Complying  with 


92  PLANT-BREEDING 

the  prevailing  belief  of  the  most  renowned  agriculturists,  who 
considered  the  breeding  of  races  as  a  slow  process  of  gradual 
improvement,  he  proposed  the  same  slow  and  almost  imper- 
ceptible changes  as  the  source  of  evolution  in  nature.  Since 
his  time  experience  and  theory  have  made  very  manifest 
progress.  Especially  the  principle  of  the  unit-characters, 
which  is  the  foundation  of  the  theory  of  the  origin  of  species 
by  mutation,  leads  us  to  the  acceptance  of  saltatory  changes 
or  so-called  sports  as  most  probably  Nature's  way  of  pro- 
ducing new  forms. 

According  to  this  theory  species  are  not  changed  into  one 
another,  but  new  forms  arise  laterally  from  the  old  stems. 
The  whole  strain  continues  unchanged  and  only  produces 
from  time  to  time  single  aberrant  individuals.  These  are 
the  real  sources  of  all  progress,  and  experience  has  shown, 
that  in  the  main  their  new  characters  are  hereditary,  and  that 
their  progeny  remains  true  to  their  new  types  even  from  its 
first  appearance. 

On  another  occasion  I  have  tried  to  show  that  in  horti- 
culture experience  comphes  almost  wholly  with  this  concep- 
tion, and  the  historical  researches  of  Korschinsky  give 
proof  of  the  accuracy  of  this  conclusion.  In  agricultural 
breeding-practice  the  production  of  new  races  is  a  more  intri- 
cate problem.  In  many  cases  their  relation  to  the  theoreti- 
cal conceptions  is  cjuite  clear,  in  others  it  is  still  surrounded 
with  doubt.  In  my  book  on  the  Mutation-theory  I  have  ex- 
plained how  the  obvious  facts  agree  with  the  idea,  but  it  was 
at  that  moment  impossible  to  remove  all  doubts,  and  so  I  pro- 
posed to  return  to  these  c|uestions  another  time.  (Mut.  Th. 
I.  p.  82.)  Five  years  have  since  elapsed  and  new  discoveries 
have  been  published  which  enable  us  to  give  a  far  more  com- 
plete analysis  of  the  agricultural  breeding  processes.  Espe- 
cially at  the  Agricultural  Experiment  Station  in  Southern 
Sweden  quite  unsuspected  facts  relating  to  the  variability  of 


NILSSON'S  DISCOVERY  93 

agricultural  crops  have  been  discovered  as  we  have  seen  in  our 
preceding  chapters.  They  are  of  a  nature  to  turn  over  all 
the  old  ideas  concerning  race-amelioration  and  give  proof 
that  the  methods  now  generally  in  use  in  Europe  are  faulty 
from  a  practical  as  well  as  from  a  scientilic  point  of  view. 
The  main  discovery  is  that  most  of  our  ordinary  agricultural 
crops  are  composed  not  only  of  elementary  species,  as  was 
long  known  before,  but  that  each  cultural  variety  contains 
hundreds  of  sharply  definite  types.  These  are  widely  dis- 
tinct from  one  another  in  botanical  characters  as  well  as  in 
those  properties,  which  determine  their  utihty  from  the 
breeder's  point  of  view,  and  thus  they  afford  a  rich  material 
for  selection. 

For  this  chapter  I  have  chosen  an  application  of  these 
discoveries  of  Nilsson  to  a  criticism  of  the  current  views 
concerning  the  bearing  of  agricultural  breeding  processes  on 
the  theory  of  evolution.  Formerly  I  urged  my  readers  to 
be  careful  not  to  trust  too  much  to  these  processes  and  to 
make  use,  in  scientific  discussions,  of  the  most  simple  and 
clear  cases  only  (]\Iut.  Theory  I,  p.  59).  The  new  facts 
now  at  hand  go  to  prove  that  the  apparently  simple  methods 
of  selection  have  been  far  more  complicated  than  their 
authors  suspected.  The  slow  and  gradual  working  up  of  a 
cereal  to  a  previously  fixed  ideal  seemed  to  be  a  process  of 
the  simplest  possible  nature.  In  reality,  however,  it  is 
composed  of  a  series  of  factors  which  the  breeders  them- 
selves have  not  recognized,  and  which  therefore  it  is  now 
often  impossible  to  discern  in  their  descriptions.  In  gen- 
eral such  an  analysis  has  been  made  practicable  by  Nilsson's 
discoveries.  Unfortunately  it  leads  to  a  less  high  apprecia- 
tion of  the  merits  of  the  breeders  (Mut.  Th.,  p.  82),  but  on 
the  other  hand  it  gives  a  stronger  support  to  the  theory  of 
the  saltatory  origin  of  species. 

Among  the  results  of  the  breeders'  activitv,  two  main 


94 


PLANT-BREEDING 


types  of  races  must  be  distinguished.  In  the  first  place, 
those  races  which  never  become  independent  of  continued 
selection,  and  for  wliich  the  seed  must  be  produced  anew 
in  each  generation  from  a  stock  of  so-called  elite  plants. 
The  other  type  embraces  those  varieties  which  after  a  sliort- 
er  or  longer  period  of  selection  become  self-dependent  and 
may  henceforth  be  multiplied  without  special  care. 

The  prototype  of  the  first  kind  is  given  by  the  sugar- 
beets.  Here  the  selection  works  with  the  ordinary  char- 
acters of  the  plant,  the  amount  of  sugar,  the  shape  of  the 
roots,  the  properties  of  the  foliage,  and  other  features.  No 
chance,  no  sport  has  produced  them,  they  are  simply  taken 
as  the  plants  are  offering  them  everywhere.  In  consequence, 
they  remain  dependent  on  selection,  and  though  a  mul- 
tipUcation  during  one  generation  without  renewed  polariza- 
tion is  often  unav(ndable,  an  inteivention  of  two  genera- 
tions is  but  seldom  allowed,  and  the  lack  of  selection  in 
more  than  two  generations  would  annihilate  nearly  all  the 
effect  of  the  w^hole  method.  This  type  of  selection  is  wholly 
intra-specilic  and  has  no  analogy  \\hale\er  with  the  origin 
of  species  in  nature. 

The  other  type  results  in  varieties  which  are  as  constant 
and  independent  as  the  best  horticultural  sorts.  In  some 
cases  they  are  known  to  originate  in  the  same  way,  by 
accidental  sports,  as  in  the  instance  of  Beseler's  oats,  losing 
their  needles.  Here  their  compliance  with  the  principle 
of  mutation  is  obvious.  In  the  large  maioritv  of  cases  how- 
ever,  including  the  most  widely  known  impro^•ements  of 
cereals  and  other  crops,  they  are  said  to  have  been  produced 
by  the  common,  slow,  and  gradual  process  of  selection. 
All  such  cases  are  surrounded  with  doubt  in  regard  to  their 
real  origin,  as  well  as  concerning  the  degree  of  self-depend- 
ency which  is  reached  at  the  end.  Often  practical  reasons 
lead  to  the  preferment  of  the  original  seed  to  one's  own 


NILSSON'S   DISCOVERY  95 

harvest,  especially  when  it  is  difficult  to  keep  the  cultures 
clean  from  vicinistic  impurities.  A  race  which  is  really 
self-dependent  may  in  this  way  seem  to  be  permanently 
related  to  the  continuous  selection  of  its  pedigree.  Such 
races  have  been  produced  at  various  times  by  Heine  in  Ger- 
many for  rye  and  wheat,  by  Drechsler  in  Gottingen  for  rye, 
by  Alokry  in  Hungary  for  wheat,  and  in  many  other  instances. 
It  is  especially  in  Germany  that  this  method  of  slow  im- 
provement is  adhered  to  and  has  given  admirable  results. 
One  of  the  best  known  instances,  and  for  which  the  liistori- 
cal  records  are  the  most  complete,  is  the  famous  rye  of 
Schlanstedt,  produced  by  Rimj)au,  which  is  now  largely 
cultivated  all  over  the  central  part  of  Germany  and  the 
northern  districts  of  France.  In  the  \'ear  1876  I  had  the 
privilege  of  visiting  Mr.  Rimpau  on  his  farm  at  Schlanstedt 
and  of  studying  his  cultures.  The  elite  of  his  new  rye  was 
standing  on  a  small  parcel  out  in  the  fields,  but  surrounded 
by  cultures  of  vegetables  and  other  plants  not  belonging  to 
the  cereals.  These  minor  cultures  occupied  a  large  sc^uare,  ^ 
which  in  its  turn  was  surrounded  b}-  a  complete  range  of 
shrubs.  Thus,  the  rye,  standing  in  midst  of  the  square,  was 
sufficiently  removed  from  the  neighboring  fields  to  insure  it 
against  possible  contamination  by  pollen  of  other  varieties. 
On  the  other  hand,  it  was  given  the  same  soil  and  exposure 
and  almost  the  same  cultural  treatment  as  the  average  cultures. 
This  race  had  been  started  by  Rimpau  nine  years  before, 
in  the  year  1867.  At  the  time  of  the  harvest  of  that  year  he 
inspected,  as  he  told  me,  a  large  number  of  his  r}-e  fields 
and  selected  all  the  ears  which  seemed  to  him  to  noticeably 
surpass  the  others.  He  brought  home  a  handful  of  them, 
repeated  the  trial,  and  mixed  their  seeds.  This  mixed  con- 
dition in  the  beginning  of  his  race  has  now  become  the 
weak  point,  where  the  whole  principle  of  his  method  is 
open  to  criticism,  as  we  shall  soon  see. 


96  PLANT-BREEDING 

The  seeds  were  sown  the  next  year,  and  in  the  harvest 
the  same  seleetion  of  the  best  ears  was  repeated.  Care 
was  taken  to  exckide  all  those  whieh,  because  of  some  ex- 
ternal condition,  would  have  been  benefited  by  more  space 
or  more  manure  than  the  rest,  and  would  have  grown  larger 
by  such  accidental  means.  No  care,  however,  was  taken  to 
isolate  the  individuals  and  to  sow  their  seeds  separately, 
the  principle  being  that  all  the  plants  belonged  to  one  race, 
and  that  this  race  had  to  be  improved.  This  j^rinciple  of 
ameliorating  a  race  without  isolating  its  possible  constituents 
seemed  at  that  period  to  be  the  right  one,  though  now  it 
can  scarcely  be  considered  as  scientifically  correct. 

Each  year,  in  the  same  way,  the  best  ears  were  chosen 
for  the  continuance  of  the  eHte  strain,  and  after  the  exclusion 
of  all  cars  of  minor  value  the  remainder  were  sown  on  a 
field  and  multiplied  witliout  further  selection  in  order  to 
produce  all  the  seed  required  for  the  sowing  of  the  whole 
farm.  It  took  three  or  four  years  to  reach  this  c[uantity. 
After  twenty  years  of  continued  selection  this  ehte  strain 
was  so  much  improved  as  to  produce  a  race  distinctly  richer 
than  the  ordinary  varieties  of  rye  in  Middle  Germany,  and 
slowly  but  gradually  it  found  its  way,  first  into  the  surround- 
ing farms,  and  afterward  over  large  parts  of  the  country. 
During  this  period  Rimpau  was  thereby  enabled  to  sell  all 
his  harvest  as  seed-grain,  obtaining  in  this  way  a  most  satis- 
factory recompense  for  his  labors.  Shortly  afterward  the 
rye  of  Schlanstedt  was  introduced  into  France,  where  it 
soon  overthrew  the  local  varieties,  especially  in  the  de- 
partments north  of  Paris.  Even  there  it  is  ordinarily  cul- 
tivated from  original  seed,  produced  directly  by  Rimpau 
or  multiplied  only  during  some  few  generations  by  seed- 
merchants. 

For  purpose  of  criticism  it  is  liighly  interesting  to  note 
how   a   French    agriculturist,    Professor   Schribaux   of   the 


Fig.  27.     A.  Rye  of    Schlanstedt,    produced  by  Wilhelm 
Rimpau,  by  slow  repeated  selection.     B.  Ordinary  rve. 

97 


98  PLANT-BREEDING 

Institut  Agronomifiue  of  Paris  explains  the  conditions  of 
keeping  the  Schlanstedt  rye  up  to  its  original  qualities.  He 
says:  'In  order  to  do  this,  care  must  be  taken  to  sow  the 
seeds  on  a  field  which  is  as  far  removed  as  possible  from  all 
other  cultures  of  rye.  Moreover,  the  field  should  be  large 
and  protected  all  around  by  a  hedge  of  trees  and  shrubs. 
Without  this  precaution  the  rye  of  Schlanstedt  would  soon 
degenerate  through  accidental  crosses  with  the  local  varieties." 
Such  crosses  would  under  any  other  conditions  be  unavoid- 
able and  soon  wholly  deteriorate  the  race  (Almanach  du 
Cultivateur  1892,  p.  69). 

From  this  judgment,  given  by  an  authority  who  has  so 
greatly  contributed  to  the  wealth  of  northern  France  by 
the  introduction  of  this  variety,  we  may  deduce  some  con- 
clusions as  to  the  constancy  of  Rimpau's  rye.  It  is  clear 
that  Schriliaux  takes  the  race  to  be  substantially  constant 
and  explains  the  necessity  of  continued  selection  only  by 
the  impending  danger  of  crosses  with  varieties  of  minor 
value.  Hence  it  follows  that  the  main  significance  of  the 
pedigree-culture  on  the  farm  of  Rimpau  must  be  the  same, 
and  that  at  least  in  later  years  his  pedigree  must  have  gained 
a  degree  of  uniformity,  which  was  in  no  need  of  any  further 
improvements.  The  real  act  of  effective  selection  is  thereby 
brought  back  to  the  first  years,  but  how  many  generations 
of  true  selection  it  has  t.iken  to  render  the  rye  of  Schlanstedt 
uniform  and  pure,  it  will  of  course  always  remain  impossible 
to  tell.  The  explanation  of  Rimpau's  success  must  there- 
fore remain  largely  hypothetical.  If  now  we  try  to  give 
such  an  explanation  on  the  ground  of  the  theory  of  mutation 
and  of  the  already  ([uoted  discoveries  of  Nilsson  we  may 
suggest  the  following:  At  the  period  when  Rimpau  started 
his  pedigree,  his  rye  fields  must  have  contained  numerous 
elementary  species,  not  observed  or  distinguished  by  him 
or  bv  anv  other  agriculturist  of   his  time.     Among  the  ears 


NILSSON'S    DISCOVERY  gy 

which  he  selected  a  goodly  number  of  these  aberrant  types 
must  of  course  have  been  represented,  since  he  selected  only 
those  which  caught  his  eye  by  some  striking  and  useful 
difference  from  the  main  type.  Of  course,  he  sought  for 
ears  of  one  and  the  same  ideal  ty[:)e,  having  a  large  number 
of  big  kernels.  But  notwithstanding  tliis,  his  handful  of 
ears  must  have  belonged  to  more  than  one  elementary 
species,  the  real  value  of  which  could  be  judged  only  in 
their  progeny.  Among  these  units  of  his  selection  some 
must  have  been  better  yielders  than  others  and  the  subse- 
fjuent  selection  of  his  twenty  years  of  pedigree-culture  must 
slowly  but  surely  have  eliminated  the  units  of  minor  worth. 
Tliis  would  result  in  the  end  in  a  complete  isolation  of  the 
best  one  of  all  the  types,  which  he  originally  but  unconscious- 
ly selected  and  mixed. 

Or  in  other  words,  Rimpau's  pedigree  culture  was  started 
as  a  mixture  of  a  number  of  exceUent  types,  and  his  yearly 
selection  has  gradually  reduced  this  number,  until  he  had 
isolated  and  purified  the  very  best  one  among  them.  This 
point  was,  of  course,  only  unconsciously  reached,  but  then 
it  must  have  made  his  rye  independent  of  all  further  real 
selection,  reducing  the  process  to  the  care  of  excluding  vi- 
cinism. 

If  this  explanation  of  Rimpau's  process  is  true,  it  of 
course  holds  good  for  all  similar  cases  of  slow  and  gradual 
improvement  of  agricultural  plants  by  selection.  Thereby 
it  would  deprive  the  theory  of  the  origin  of  species  by  slight 
and  continuous  changes  of  its  last  support  in  the  realm  of 
the  vegetable  kingdom. 

It  remains  to  be  shown  that  the  new  facts  give  sufficient 
proof  of  the  accuracy  of  this  suggestion.  These  facts  may 
be  grouped  under  three  heads.  First,  the  general  occur- 
rence of  elementary  species  and  their  constancy.  Secondly, 
a   comparison   of   the   value   of   liuctuating   variability   and 


loo  PLANT-BREEDING 

mutability  among  cereals,  and  in  the  third  place,  the  research- 
es of  Nilsson,  which  have  given  the  leading  principle  for  my 
suggestion. 

Our  first  point  is  now  becoming  generally  recognized. 
The  researches  of  Jordan  and  of  Wittrock  show  the  existence 
of  races  for  the  species  of  the  genus  Viola.  Other  notable  in- 
stances are  those  of  Draba  verna,  of  Capsella  Heegeri,  of 
the  Xantliium  Wootoni,  a  variety  with  half  the  original 
number  of  spines  on  its  burs,  and  many  others. 

For  myself,  I  have  had  opportunities  to  test  the  constancy 
of  such  elementary  forms  and  in  some  instances  even  at  the 
period  of  their  very  first  discovery.  Two  local  evening- 
primroses,  up  to  the  present  time  occurring  only  on  a  field 
near  Hilversum,  where  they  are  growing  among  the  common 
Oenothera  Lamarckiana,  have  given  proof  of  their  absolute 
constancy  in  my  cultures.  They  are  the  O.  IjevifoUa  and 
O.  brevistylis,  both  of  wliich  are  still  seen  to  thrive  on  their 
small  native  locality.  Other  instances  are  the  cruciate 
form  of  the  ordinary  European  primrose,  (Enothera  biennis 
and  an  analogous  variety  of  the  willow-herb,  Epilobium 
hirsutum.  Many  other  instances  could  easily  be  added. 
The  conclusion  seems  warranted  that  elementary  forms 
may  be  found  in  nearly  all  systematic  species,  and  are  as 
constant  as  the  latter  have  always  been  supposed  to  be. 
These  facts  give  a  strong  presumption  that  the  same  rule 
may  hold  good  for  the  rye-cultures  of  Rimpau. 

My  second  point  relates  to  the  question  of  the  part  which 
fluctuating  variabihty  and  mutability  may  have  played  in 
the  selection-culture  of  Rimpau.  i\n  exact  notion  of  the 
first  phenomenon,  as  stated  by  the  works  of  Quetelet  (1870) 
and  Galton  (1889)  found  its  way  into  botanical  investiga- 
tions about  the  year  1894,  or  nearly  twenty-five  years  after 
Rimpau  started  his  pedigree  of  r}T.  In  his  time,  therefore, 
no  distinction  of  this  kind  could  be  made,  and  it  is  only 


NILSSON'S   DISCOVERY  loi 

natural  that  he  took  his  selected  specimens  to  be  the  extremes 
of  ordinary  variability  (1867). 

Tliis  point  of  view,  and  this  lack  of  distinction  between 
the  now  so  clearly  contrasted  processes  has  prevailed  for  a 
long  time  among  agriculturists.  As  an  instance  I  may  quote 
the  work  of  Willct  M.  Hays,  now  in  Washington,  which, 
though  younger  than  the  researches  at  Svalof,  has  been 
conducted  independently  (1899  Bull.  No.  62.,  Agric.  Exp. 
Station,  Minnesota).  He  has  improved  the  wheat  of 
Minnesota  by  breeding  from  the  local  Fife  and  Blue  Stem 
races,  some  better  and  more  yielding  varieties,  wliich  have 
now  largely  supplanted  the  old  types.  Besides  liis  practical 
results,  he  has  given  some  theoretical  discussions,  in  which 
he  assumes  a  relation  of  his  chosen  mother  plants  to  the 
fluctuating  variability  and  considers  them  extremes  in  the 
curves  which  constitute  the  law  of  Quctclet.  "In  each  one 
thousand  plants  of  wheat,"  he  says,  "there  are  a  few 
phenomenal  yielders,  and  the  method  of  single-seed  planting 
makes  it  practical^le  to  secure  these  exceptional  plants,  and 
from  these  new  varieties  can  be  made"  (p.  429).  But 
according  to  our  present  knowledge,  the  isolation  of  such 
plants,  if  they  were  truly  extremes  of  fluctuating  variability, 
would  lead  to  a  regression  to  mediocrity,  as  it  has  been 
called  by  Galton,  and  not  to  constancy  nor  to  an  exact  keep- 
ing up  of  the  extreme  type.  Therefore  the  supposition  is 
allowed  that  the  phenomenal  yielders  of  Hays  were  in  reality 
representatives  of  distinct  elementar}^  species,  which  had 
been  hidden  until  his  time.  His  method  of  selecting  enabled 
him  to  single  them  out,  and  his  new  principle  of  single- 
seed  planting,  which  led  him  to  his  high  achievements,  at 
the  same  time  pointed  out  the  way  for  an  explanation  on 
the  basis  of  our  present  \iews  concerning  the  different  types 
of  variability. 

It  would  take  me  too  long  to  describe  the  methods  and 


I02  PLANT-BREEDING 

cultures  of  the  ^linncsota  Experiment  Station,  and  I  may 
assume  that  their  leading  principles  and  practical  results 
are  well  kno\\ii.  But  I  wish  to  point  out,  that  exactly  in 
the  principle  of  sowing  the  seeds  of  indi\idual  selected  plants 
separately,  Hays  gained  a  distinct  advantage  over  the  slow 
process  of  Rimpau  and  the  other  (jcrman  breeders.  He 
found,  by  his  method,  that  the  isolated  strains  are  at  once 
constant  and  pure.  They  had  only  to  be  multiplied  in 
order  to  give  a  new  race.  Of  course,  the  different  mother 
plants  had  to  be  compared  in  their  progeny,  and  among  a 
large  number  of  such  new  pedigree-races  only  one  or  two 
were  found  to  be  of  the  vcTy  best.  The  remainder  had  to 
be  rejected,  and  only  those  few  most  excellent  ones  could  be 
introduced  with  advantage  into  the  field-cultures  of  the 
state. 

If  now  we  compare  this  principle  of  Hays  with  the 
method  of  Rimpau  we  find  that  the  American  breeder  by 
one  single  choice  isolated  the  ver}'  best  strains  and  observed 
them  to  be  constant  and  pure.  The  German  breeder,  on 
the  other  hand,  by  selecting  a  number  of  ears,  must  have 
gotten  an  impure  race,  and  needed  a  long  succession  of 
years  and  a  constantly  repeated  selection  to  attain,  in  the 
end,  the  same  result. 

Hence  we  may  presume  that  if  Rimpau,  in  starting  his 
experiments,  forty  years  ago,  had  had  at  his  disposal  our 
present  knowledge  of  variability,  he  would  have  sown  the 
kernels  of  his  selected  ears  separately  and  selected  at  once 
among  the  resulting  strains  the  very  one  which  now  bears 
the  name  of  his  farm.  No  continuous  culture  and  repeated 
selection  would  have  been  needed,  and  the  seemingly  slow 
and  gradual  improvement  of  a  race  by  selection  would  have 
been  avoided. 

The  proof  of  this  assertion  can  be  given,  as  has  been 
said  in  the  beginning,  by  means  of  the  magnificent  experi- 


o  o  cr; 


103 


I04  PLANT-BREEDING 

ments  of  Nilsson  at  the  Swedish  Agricultural  Experiment 
Station  at  Svalof .  Though  working  only  in  the  interest  of  the 
practical  breeder,  he  appHed  to  his  selection  thoroughly 
scientific  methods  and  has  arrived  at  the  clear  and  unex- 
pected conceptions  of  the  variability  of  cereals  and  other 
large  agricultural  crops,  wliich  we  have  exposed  in  our 
previous  chapters.  Summing  up  their  contents  in  a  few 
sentences,  I  have  first  to  recall  the  practical  results  and 
the  numerous  new  and  [productive  races,  which  have  been 
originated  at  Svalof  and  are  now  rapidly  finding  approval 
with  the  agriculturists  of  Sweden,  and  even  of  Germany  and 
other  countries.  For  scientific  purposes  they  give  proof  of 
the  validity  of  the  methods  employed  at  that  station,  and  of 
the  accurate  nature  of  the  principles  involved  therein. 

Nilsson  at  first  tried  the  usual  German  method,  but 
soon  found  that  it  yielded  its  results  only  in  exceptional 
cases  and  could  not  be  appHed  to  all  the  needs  of  the  agri- 
culturists (1885-1891).  He  then  changed  his  principle  and 
sowed  the  kernels  of  numerous  selected  ears  separately  or 
in  small  groups  (1891-1892).  The  result  was  thoroughly 
decisive,  for  all  the  parcels  grown  from  mixed  seeds  gave 
a  mixed  progeny,  and  only  those  which  were  derived  from 
one  single  ear  each  gave  a  pure  and  uniform  culture.  This 
unexpected  phenomenon  was  at  once  made  the  basis  for 
further  experiments  and  in  numerous  sowings,  where  each 
was  derived  from  one  single  plant,  the  strains  were  almost 
always  found  pure  and  constant.  The  only  exceptions  were 
those  in  which  a  hybrid  ear  had  been  accidentally  chosen. 
Here  of  course  the  ordinary  sphttings  of  hy1)rid  progeny 
were  observed,  but  in  choosing  among  their  products,  con- 
stancy could  be  reached  in  many  instances. 

Therefore  Nilsson's  principle  for  all  breeding  purposes 
is  now  to  derive  his  strains  from  single  mother  plants.  Only 
such  strains  give  pure  breeds.     A  second  discovery  made 


NILSSON'S   DISCOVERY  105 

at  Svalof,  and  equally  valuable  for  practice  and  for  science, 
was  that  of  the  almost  astonishing  richness  in  elementary 
species  among  our  agricultural  crops.  Every  cultivated 
species  seems  to  embrace  something  like  a  hundred  of  them, 
and  the  cereals  were  found  to  include  even  several  hundreds 
in  each  of  the  older  species.  Moreover  the  differences 
between  these  elementary  forms  are  so  great  that  they  cover 
nearly  the  whole  field  of  the  wants  of  the  practical  agricul- 
turist, or,  in  other  words,  by  carefully  searching  the  field, 
in  almost  every  case  a  plant  may  be  found  which  complies 
with  the  ideal  sought  for.  From  such  a  plant  a  pure  and 
constant  race  may  be  derived  without  other  means  than 
that  of  isolating  and  multiplying  its  progeny.  No  special 
culture  and  no  repeated  selection  is  needed,  the  only  care 
being  to  protect  the  race  against  vicinism.  On  the  basis 
of  these  facts  Nilsson  has  founded  an  elaborate  method  of 
selecting  original  plants  for  his  pedigree-cultures  and  of  com- 
paring their  value  for  practical  purposes.  But  though  this 
process  is  now  the  prominent  part  of  his  work,  it  has  no 
direct  bearing  upon  the  signification  of  the  methods  of 
Rimpau  and  other  German  breeders,  and  so  we  may  leave 
it  here  out  of  consideration. 

Our  explanation  of  Rimpau's  method  now  loses  its  hypo- 
thetical aspect.  For  since  it  is  proven  that  the  ordinary  rye- 
fields  contain  hundreds  of  elementary  species,  and  among 
them  many  of  superior  quahty,  it  is  clear  that  Rimpau  must 
have  had  an  assemblage  of  such  types  in  his  original  hand- 
ful of  selected  ears.  To  him  they  may  have  seemed  alike, 
but  they  must  have  been  in  reality  of  very  different  value. 

His  slow  process  of  selecting  must  have  singled  out  in 
the  long  run,  the  very  best  one  from  among  them.  Once 
isolated,  this  type  yielded  a  constant  race,  which  became 
independent  of  all  further  selection. 

The  German  breeding  process  has  always  been  one  of  the 


io6  PLANT-BREKDINCr 

most  important  arguments  for  the  prevailing  selection-theory 
and  was  of  late  considered  its  last  botanical  support.  By 
means  of  the  discoveries  of  Hays  and  of  Nilsson  this 
support  has  now  been  broken  down,  and  the  \actory  of  the 
theory  of  a  saltatory  origin  of  species  can  no  longer  be 
doubted. 


Ill 

ON   CORN  BREEDING 

In  Europe  the  smaller  cereals  constitute  the  prevailing 
crops,  but  in  the  United  States  of  America,  corn  is  king, 
as  the  phrase  goes. 

Yearly  about  2500  million  bushels  of  Indian  corn,  with 
a  value  of  $1,000,000,000,  are  produced  in  this  country, 
constituting  almost  eighty  per  cent  of  the  world's  total  crop. 
Of  this  more  than  1500  million  bushels  arc  fed  to  cattle  and 
other  meat-producing  animals,  the  remainder  being  partly 
exported  and  partly  used  for  different  industrial  purposes. 
The  total  number  of  beef  cattle  in  the  United  States  was 
officially  estimated  in  1904  at  43,500,000,  with  a  total  value 
of  $660,000,000. 

Over  a  hundred  different  commercial  products  and  about 
fifty  kinds  of  food  are  derived  from  corn  and  its  various 
constituents,  the  glucose  factories  alone  consuming  over 
50,000,000  bushels  of  corn. 

There  can  be  no  doubt  that  corn  is  the  most  valuable 
crop  in  the  United  States.  Cotton,  of  course,  bears  the 
palm  as  a  money  crop,  but  corn  is  the  main  supply  of  food, 
directly  as  well  as  under  the  form  of  meat.  No  single  cereal 
is  of  the  same  high  importance,  and  the  agriculture  of  the 
principal  states  of  the  Middle  West  is  almost  wholly  depen- 
dent upon  the  raising  of  corn. 

Illinois  stands  first,  but  Iowa,  Missouri,  Kansas,  Ne- 
braska, and  some  others  deserve  as  well  their  name  of  the 
corn  states.  In  Indiana  the  average  crop  is  ;^;^  bushels  per 
acre,  a  bushel  containing  in  round  numbers  100  ears  and 
commonly  shelhng  out  56  pounds. 

On  account  of  tliis  pre-eminent  importance,  all  questions 
concerning  the  possible  means  of  increasing  the  crop  of  corn 


io8  PLANT-BREEDING 

are  manifestly  of  the  highest  vakie.  Our  discussion  of  the 
different  metliods  of  improving  cereals  has  for  this  reason 
to  be  completed  by  an  inquiry  in  how  far  and  on  what 
points  the  principles  discovered  and  elaborated  in  Europe 
can  advantageously  be  considered  in  the  selection  of  tliis 
dominant  American  crop. 

In  thi'  corn  states  the  production  of  corn  has  since 
some  years  ago  reached  its  higliest  degree  of  development, 
as  far  as  its  acreage  is  concerned.     Almost  all  the  land  suit- 


Fig.  29.     Breeding  block  of  corn  which  has  been  bred  for  high  oil  content 
on  the  farms  of  Funk  Bros.  Seed  Co.,  Bloomington,  111. 

able  for  corn  growing  has  been  given  to  this  crop.  Locally, 
some  increase  of  the  area  may  still  be  possible,  but  it  is  of 
no  real  importance  for  the  total  amount  of  the  crop. 

Hence,  it  follows  that  an  increase  of  the  harvest  can  be 
obtained  only  by  an  augmentation  of  the  yield  per  acre, 
and  since  the  demand  for  corn  is  incessantly  increasing  and 
the  prices  are  becoming  correspondingly  higher,  the  question 
how  to  increase  this  yield  has  become  a  most  urgent  one. 
The  land  values  are  constantly  rising,  and  handsome  profits  are 
possible,  but  to  secure  them  better  methods  must  be  employed. 


log 


no  PLANT-BREEDING 

The  use  of  fertilizers,  more  careful  processes  of  prepar- 
ing the  land  and  handhng  the  seed  and  the  plants,  and  a 
proper  choice  of  the  seed-grain  are  the  acknowledged  means 
by  wliich  to  attain  this  end 

Of  course,  in  these  lectures  I  am  concerned  only  with  the 
questions  relating  to  variabiUty  and  selection.  But  no  crop 
is  more  responsive  to  careful  selection  of  the  seed  than  corn. 
According  to  the  condition  of  the  land,  the  treatment  of 
the  field  may  be  of  first  importance,  but  good  seed  will 
always  add  considerably  to  the  yield,  and  the  more  so,  the 
better  the  condition  of  the  soil  and  the  care  given  to  its 
culture. 

Some  farmers  are  producing  60  to  70  bushels  per  acre 
every  year,  while  their  neighbors  are  contented  with  an 
average  harvest  of  30  to  35  bushels.  In  favorable  cases  the 
product  might  easily  be  increased  to  a  hundred  bushels  per 
acre  and  even  more. 

As  a  rule,  howe^•er,  the  c(jrn  yield  per  acre  is  gradually 
decreasing,  at  least  in  some  of  the  leading  states.  In  Ohio 
the  period  i8()0  to  1899  shows  a  falling  off  of  33  bushels  as 
compared  with  the  i)revious  ten-year  period.  But  in  Indi- 
ana, where  the  interest  in  corn  selection  is  rapidly  growing, 
the  average  yield  per  acre  has  increased  during  the  same 
time  by  12,8  per  cent,  and  in  IlHnois,  which  has  started  the 
principle  of  individual  ear  selection,  the  yield  per  acre  of 
corn  has  increased  to  22  ])er  cent  more  than  in  the  ten  years 
preceding  the  introduction  of  this  new  method. 

The  recent  discoveries  made  at  the  Agricultural  Experi- 
ment Station  of  Sweden  will,  no  doubt,  some  day  exercise 
a  notable  influence  on  the  American  processes  of  corn- 
Vjreeding.  In  some  points  they  are  in  full  agreement  with 
them,  but  since  they  are  founded  on  more  elaborate  scien- 
tific methods,  they  may  facilitate  the  understanding  of  the 
processes  now  in  use. 


J> 


» *  i  i  •'' 


V-  ^:i 


A 


C 


3 


Fig.  31.     DilTerent  types  of  corn.     A.  King  Philipp,  a  variety  of  flint  corn. 
B.  Giant  yellow  dent  corn.     C.  Rice  popcorn.    D.  Dwarf  popcorn. 


112  PLANT-BREEDING 

In  some  of  the  bulletins  of  the  agricultural  experiment 
stations,  dealing  with  the  improvement  of  corn,  it  has  been 
pointed  out  that  we  do  not  yet  understand  many  of  the  prin- 
ciples underlying  corn-breeding,  but  that  on  the  other  hand 
it  is  to  the  interest  of  each  corn-grower  to  obtain  as  com- 
plete a  knowledge  on  this  point  as  possiljle,  in  order  thereby 
to  bring  the  factors  of  his  selection  under  his  control. 

From  a  scientific  point  of  view,  however,  there  can  be 
little  doubt  that  the  same  laws  that  govern  the  variability 
and  the  selection  of  cereals  in  general  control  the  corres- 
ponding phenomena  for  corn,  too,  and  that  the  existing 
differences  are,  as  a  fact,  only  due  to  those  ])lain  and  easily 
recognizable  characters  which  contrast  corn  with  the  smaller 
cereals. 

For  this  reason  I  propose  to  give  a  description  of  the 
facts  of  variability  and  the  methods  of  selection  of  corn, 
based  on  the  principles  evolved  for  cereals  in  my  previous 
chapters.  I  shall  conscientiously  describe  the  facts,  but  shall 
rely  in  their  appreciation  partly  on  the  obtained  results,  and 
partly  on  a  comparison  with  the  Swedish  and  German  prin- 
ciples. In  doing  so  my  chief  aim  is  to  awaken  the  interest 
of  all  those  who  are  in  one  way  or  another  concerned  in 
corn-breeding,  for  a  study  of  analogous  cpiestions  in  other 
crops. 

The  study  of  variability  is  the  basis  of  all  selection. 
The  more  we  are  enabled  to  discern  slight  differences  and 
to  appreciate  their  possible  industrial  value,  the  better  we 
shall  be  guided  in  our  choice. 

Moreover,  the  term  variability  covers  so  wide  a  range 
of  phenomena,  and  the  significance  of  the  single  constituents 
of  this  large  group  for  the  purpose  of  race-breeding  is  so 
widely  cHffercnt,  that  it  is  of  pre-eminent  importance  to  have 
a  critical  survey  of  the  most  obvious  cases. 

Evervbodv  knows  that  corn  is  one  of  the  most  multiform 


Fig.  32.  A.  Sweet  corn,  a  cob  with  a  staminate  upper  part  and 
with  some  few  kernels  in  top.  B,  C.  Parts  of  a  tassel  of  flint  corn 
bearing  staminate  spikelets  and  kernels. 

113 


114  PLANT-BREEDING 

species.  It  embraces  seven  types  which  are  different  enough 
to  be  considered  by  some  authors  as  the  equivalent  of  sys- 
tematic species.  Each  of  these  groups  includes  a  number 
of  varieties  or  sub-races,  and  these,  in  their  turn,  are  by  no 
means  uniform,  but  offer  to  the  experienced  eye  an  utter 
chaos  of  individual  variations. 

The  significance  of  the  main  types  and  their  most  evi- 
dent varieties  is  nowadays  fairh-  well  estabUshed,  but  it 
is  the  almost  inexhaustible  individual  variability  within  the 
varieties  that  gives  the  material  for  selection. 

The  main  types  are  six  in  number,  viz. :  The  pod  corns, 
the  pop  corns,  the  tlint  corns,  the  dent  corns,  the  soft  corns, 
and  the  sweet  corns.  In  the  pod  corns  or  Zea  Mays  tuni- 
cata  the  kernels  of  the  ear  are  enclosed  in  husks,  constitu- 
ting together  a  pod  for  each  single  kernel.  This  is  the  form 
which  was  assumed  by  Darwin  to  Ijc  the  nearest  relative  of 
the  hvpothetical  ancestors  of  the  whole  group,  since  corn  is 
the  only  species  in  the  family  of  the  grains,  which  possesses 
naked  kernels. 

The  pop  corn  is  easily  recognized  by  the  small  size  of 
the  kernels  and  ear  and  by  the  excessive  proportion  of  the 
hornv  or  corneous  endosperm,  which,  in  the  best  varieties,  is 
so  well  developed  that  it  wholly  excludes  the  starchy  tissues. 
This  gives  the  property  of  popping,  by  which  process  the 
kernel  is  burst  and  the  contents  turned  inside  out.  The 
rice  pop  corns,  with  pointed  kernels,  are  among  the  best- 
known  races  of  this  group. 

The  flint  corns  have  a  well- developed  starchy  tissue  en- 
closed by  the  horny  endosperm.  This  latter  varies  in  thick- 
ness with  the  varieties  and  causes  the  kernels  to  become  too 
hard  when  dry  for  cattle  to  eat  them  without  their  being 
ground.     Thence,  the  Latin  name  "indurata.  " 

The  dent  corns,  Zea  ^lays  indentata,  are  easily  recog- 
nized by  the  indentation  on  their  outer  surface.     This  dc- 


Fig.  33.     A  highly  ramified  cob  of  com 
115 


ii6  PLANT-BREEDING 

prcssion  is  caused  by  the  shrinkage  of  the  starchy  matter 
in  drying.  The  dent  varieties  are  almost  the  exclusive  corn 
crop  of  the  corn  states  and  are  of  supreme  value  in  the  feed- 
ing of  cattle;  they  are  more  numerous  than  all  the  varieties 
of  the  five  remaining  groups  taken  together. 

The  soft  corns,  Zea  Mays  amylacea,  have  no  corneous 
endosperm,  as  their  name  indicates.  The  kernels,  however, 
shrink  uniformly  and  do  not  become  wrinkled  in  drying. 
This  group  includes  some  of  the  oldest  varieties,  as,  for  in- 
stance, the  mummy  corns  of  Peru  and  Chile,  and  the  very 
largest- kerncled  type,  the  Cusco. 

The  sweet  corns,  or  Zea  Mays  saccharata,  are  character- 
ized by  their  wrinkled  and  more  or  less  translucent  seed. 
This  condition,  however,  is  not  caused  by  the  horny  part  of 
the  kernel,  ]:)ut  l^y  the  starchy  tissue  in  which  the  starch  is 
almost  wholly  absent.  It  is  replaced  by  a  sweet  constituent 
or  kind  of  sugar,  belonging  to  the  group  of  the  dextrines. 
It  is  mainly  grown  for  table  use  and  for  canning  purposes, 
the  grain  being  canned  before  becoming  ripe.  Maine  and 
New  York  are  the  principal  states  for  this  culture,  which, 
however,  extends  all  along  the  Atlantic  coast. 

In  each  of  these  six  main  groups  there  are  a  number  of 
varieties  which  are  partly  distinguished  by  the  forms  of  the 
kernels,  whether  broad  or  deep,  partly  by  the  proportion  of 
the  horny  and  the  starchy  part  of  the  endosperm,  and  partly 
by  many  other  subordinate  marks.  E.  L.  Sturtevant,  in 
liis  Varieties  of  Corn  (U.  S.  Dcpt.  of  Agriculture,  1899,  N. 
57)  enumerates  300  varieties  of  dent  corn,  70  of  flint,  60  of 
sweet  corn,  and  so  on.  These  varieties  or  sub-races  are 
cultivated  under  different  names,  and  their  characters  are 
said  to  be  constant  and  more  or  less  sharply  defined,  not 
changing  under  the  influence  of  soil,  cHmate,  or  treatment. 
Among  the  dent  corns  the  dimple-dented,  crease-dented, 
pinch-dented,  and  ligulate-dented  may  be  cited  as  instances. 


ON   CORN   BREEDING  117 

But  almost  every  one  of  these  varieties  is  all  but  uniform. 
They  include  all  kinds  of  variations,  both  in  the  shape  of 
the  kernel  and  the  ear,  and  in  the  mode  of  growth  and  vege- 
tative characters  of  the  stalks  and  foHage.  The  differences 
among  these  minor  types  within  a  given  variety  are  often  as 
great  as  those  which  distinguish  the  varieties  themselves. 
As  a  fact,  the  varieties  are  mixtures  of  a  larger  or  lesser  num- 
ber of  constituents,  the  same  sub-types  recurring  often  in 
more  than  one  so-called  variety. 

Moreover,  many  of  these  varieties  are  subjected  to  abnor- 
mal deviations  from  the  type  or  so-called  monstrosities, 
including  the  most  widely  divergent  forms.  Stalked  and 
branched  ears,  male  side-spikes  on  the  ears,  kernels  in  the 
tassels,  cockscomb- ears,  hermaphrodite  flowers,  variegated 
leaves,  and  many  other  features  are  the  well-known  instances. 
They  are  without  practical  value,  and  their  hereditary  char- 
acters have  accordingly  been  only  imperfectly  studied. 
Such  study  should  not  be  neglected,  however,  since  the  bar- 
ren stalks,  which  often  cause  enormous  losses,  seem  to  belong 
to  the  same  group  and  to  obey,  in  their  manner  of  inheri- 
tance, the  same  laws.  But  with  this  phenomenon  I  shall 
have  to  deal  later. 

The  variability  within  the  varieties  is  the  main  source  of 
all  selection,  and,  as  such,  deserves  our  careful  attention.  The 
distinguishing  marks  are  many,  but  often  so  minute  as  to  be 
hardly  fit  for  description.  Often  they  are  the  same  as  those 
between  distinct  varieties,  and  in  such  cases  different  varie- 
ties may  simply  be  chfferent  mixtures  of  mainly  the  same 
constituents.  In  some  cases  the  same  varieties  may  even  be 
cultivated  locally  under  different  names.  Mixing  of  color 
is  the  easiest  indication  of  such  a  mixing  of  sub-types;  it  has 
attracted  the  eye  of  the  farmers  for  a  long  time,  and  often 
led  them  to  some  kind  of  primitive  selection,  preferring  a 
pure  color  to  the  mixture. 


ii8  PLANT-BREEDING 

In  selection,  uniformity  is  one  of  the  main  purposes, 
but  the  shape  and  color  of  the  ears,  their  butt  and  tip  ends, 
the  number  and  direction  of  the  rows,  the  furrows  between 
the  rows  and  many  other  points  have  to  be  considered.  It 
is  only  by  an  actual  study  of  these  variations  that  a  farmer 
may  become  familiar  with  all  the  different  types.  It  would 
be  quite  superfluous  to  try  to  describe  them  here,  the  more 
so  as  we  shall  have  to  (|Uote  a  number  of  instances,  when 
dealing  with  the  work  of  selection. 

Perhaps  the  most  important  discovery  wliich  has  been 
made  concerning  these  minor  variations,  is  that  of  their 
constancy.  All  the  kernels  of  a  selected  ear  have  the  same 
quahties,  provided,  of  course,  that  cross-polHnation  has  been 
sufficiently  excluded.  This  is  easily  seen  in  their  visible  or 
physical  quahties,  but  the  experiments  of  Hopkins  have 
shown  that  the  same  rule  prevails  for  the  chemical  consti- 
tution, including  the  relative  development  of  the  main  indus- 
trial constituents.  Moreover,  it  is  true  for  the  hereditary 
([uahties. 

In  the  first  place,  direct  ex]:)eriments  have  shown  that 
neither  the  yield  nor  the  equality  of  the  grain  is  essentially 
affected  by  choosing  the  seed-grains  from  the  butt  end,  the 
middle,  or  the  tip  of  an  ear.  Furthermore,  it  is  now  cus- 
tomary, as  we  shall  soon  see,  to  sow  the  kernels  of  selected  ears 
in  single  rows,  each  ear  to  a  row,  and  by  this  method  the 
fact  of  the  individuality  of  the  rows  lias  become  quite  con- 
spicuous. A  whole  row,  grown  from  the  kernels  of  a  single 
ear,  may  produce  numerous  barren  stalks,  or  weak  plants, 
or  small  ears  with  imperfect  yield,  or  be  excellent  in  strength, 
productivity,  and  uniform  in  other  peculiar  characteristics. 
This  fact  is  now  the  acknowledged  basis  of  the  main  prin- 
ciple of  com  selection. 

From  these  and  many  other  concurring  observations  we 
may  conclude  that  the  variability  of  corn  within  the  varieties 


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119 


1 20  PLANT-BREEDING 

mentioned  is  of  the  same  nature  as  that  observed  at  Svalof 
for  the  other  cereals,  and  described  in  our  previous  lectures. 
Thus  the  varieties  are  to  be  considered  as  built  up  of  quite 
numerous  elementary  forms,  each  of  which  is  essentially 
uniform  and  constant.  The  cross-polUnation  must,  of 
course,  obscure  tliis  fact  to  some  extent,  but  cannot  annilii- 
latc  it.  As  soon  as  such  an  elementary  form  is  sufficiently 
isolated  and  multiplied  so  that  its  progeny  may  fertilize  it- 
self exclusively,  a  uniform  and  constant  race  will  be  obtained. 
Variability  will  then  be  hmited  to  the  smaller,  Init  unavoid- 
able changes,  wliich  climatic  and  environmental  conditions 
will  always  evoke,  even  in  the  most  purely  bred  races.  The 
nature  of  these  so-called  fluctuations  we  shall  soon  have  to 
consider,  but  for  selection  they  are  only  of  secondary  impor- 
tance. 

The  princi]ile  of  selection  at  the  '  Svalof  Ex])eriment 
Station  consists  in  the  search  for  such  elementary  forms, 
and  in  their  isolation  and  subse([uent  comparative  trial. 
No  purifying  and  no  fixing,  or  in  other  words,  no  subsequent 
or  continuous  selection  is  needed,  provided  the  chosen  ears 
are  not  hybridized.  Man  cannot  originate  these  variations, 
nor  can  he  essentially  improve  them.  He  must  simply  be 
on  the  alert  to  recognize  and  isolate  them  and  to  compare 
their  progeny  with  the  main  strain.  In  the  same  way  the 
problem  of  corn-breeding  is  to  recognize  these  elementary 
races.  All  success  depends  upon  finding  the  best  among 
them  and  on  thus  taking  complete  advantage  of  the  variabil- 
ity already  existing  in  the  fields.  Even  the  races  with  spe- 
cial characters,  as,  for  instance,  those  with  a  high  yield  of 
oil  or  of  protein,  have,  as  a  fact,  been  secured  in  this  same 
way. 

Corn,  however,  chffcrs  from  the  other  cereals  in  some 
very  important  points.  Two  of  them  are  now  to  be  consid- 
ered.    One  is  the  open  pollinized  condition,  and  the  other 


Fig.  3v     A.  Tassel  of  corn,  llowering  and  producing  the  anthers  from  the 
spikelets.     B.  Cob  in  the  husks,  producing  the  silks, 


122  PLANT^BREEDING 

is  the  large  size  of  the  ears  and  their  enormous  number  of 
seeds. 

On  a  normal  individual,  the  female  or  pistillate  flowers 
are  combined  on  the  ears,  and  at  the  time  of  tlowcring  the 
pistils  or  silks  are  protruded  from  the  top  of  the  husks.  The 
wind  has  to  carry  the  pollen  to  them.  The  male  or  stam- 
inate  inflorescences  are  the  tassels  on  the  top  of  the  stalks. 
Each  flower  contains  tliree  stamens,  and  each  tassel  pro- 
duces about  20,000,000  to  50,000,000  grains  of  pollen.  By 
far  the  largest  (quantity  of  these  is,  of  course,  lost,  being  depos- 
ited on  the  foliage  or  falling  to  the  ground.  But  a  sufticient 
number  are  transferred  to  the  silks  to  insure  the  complete 
fertilization  of  the  ears.  This,  liowever,  is  not  reached  at 
once,  but  several  days  are  needed  for  the  process.  The  silks 
do  not  all  appear  at  the  same  time,  those  of  the  uppermost 
kernels  being  the  first.  Moreover,  they  continue  growing 
until  a  considerable  length  is  reached.  The  diffusion  of 
the  pollen  mainly  takes  place  early  in  the  morning,  when 
the  scales  and  anthers  open  under  the  influence  of  the  rays 
of  the  sun.  Four  or  five  days  are  usually  reipiired  to  pollin- 
ate all  the  silks  of  an  ear. 

It  is  evident  that  only  a  part  of  the  })ollen  will  fall  upon 
the  silks  of  the  same  plant.  This  is  called  self-pollination 
or  self-fertilization.  The  stronger  the  wind  blows,  the  great- 
er the  quantity  that  drifts  to  other  cars,  thereby  insuring 
cross-fertilization.  Pollen  will  drift  in  this  way  over  long 
distances,  and  is  known  to  have  been  carried  by  the  wind 
over  more  than  a  thousand  feet  of  surface.  If  kernels  of  one 
mother  ear  are  sown  close  to  one  another  the  pollen  may  be 
transferred  to  the  children  of  the  same  mother,  and  this  is 
called  close-pollination. 

The  effects  of  cross-fertiHzation  often  can  be  seen  when 
different  varieties  are  cultivated  on  adjacent  fields.  Some 
color-varieties  and  the  sweet  corns  are  exceedingly  liable  to 


ON    CORN   BREEDING 


123 


this  phenomenon.  In  these  cases 
the  effects  may  be  observed  cU- 
rectly  on  the  ears,  without  await- 
ing the  next  generation.  This 
is  ckie  to  the  phenomenon  known 
as  double  fertiUzation  and  which 
has  been  cUscovered  only  lately. 
The  endosperm,  in  order  to  devel- 
op, must  be  fertilized  as  well  as 
the  germ,  and  this  is  l^rought 
about  by  the  tubes  of  the  pollen 
grains  carrying  each  two  male 
elements  or  cells,  one  destined  for 
the  germ  and  the  other  for  the 
endosperm.  Hence  we  see  that 
in  cross-pollinizing  tlie  endo- 
sperm assumes  a  hybrid  nature 
as  well  as  the  germ.  In  ordinary 
cases  this  condition  does  not  be- 
tray itself  by  any  visible  mark. 
In  crossing  sweet  corn  with  dent 
or  flint  corn,  the  hybrid  endo- 
sperm assumes  the  characters  of 
the  male  parent.  Thus,  when  an 
ear  of  sweet  corn  is  partly  fertil- 
ized by  a  dent  corn,  we  shall  find 
on  it,  after  ripening,  some  starchy 
kernels  among  the  wrinkled  and 
translucent  majority.  It  is  evi- 
dent that  the  number  of  these 
aberrant  kernels  will  correspond 
to  the  number  of  threads  in  the  silks  which  are  thus  cross- 
poUinated,  and  the  number  of  the  differing  kernels  is  to  be 
considered  a  direct  measure  of  the  proportion  of  alien  pollen 


Fig.  36.  Sweet  corn,  ^\^th 
scattered  starchy  kernels,  pro- 
duced by  partial  cross-pollina- 
tion. 


124  PLANT-BREEDING 

deposited  on  the  silk.  In  close  proximity  this  number  will 
often  surpass  that  of  the  normal  kernels,  and  by  artificial 
cross-pollination  all  the  kernels  on  an  ear  of  sweet  corn  may 
be  induced  to  become  starchy.  It  is  a  simple  method  of 
measuring  the  degree  of  transportation  of  pollen  l)y  the 
wind,  and  wherever  a  field  of  sweet  corn  is  near  a  culture  of 
dent  corn,  the  inspection  of  the  ears  may  give  us  an  idea  of 
the  significance  of  this  transportation. 

All  the  starchy  kernels  on  a  partly  cross-pollinated  ear  of 
sweet  corn  have  hybrid  germs,  since  they  were  fertiUzcd  by  the 
contents  of  the  same  pollen  tube  as  the  endosperm.  By  this 
means  the  hybrid  kernels  may  be  recognized  and  eliminated 
in  such  cases,  and  thus  the  strains  of  sweet  corn  are  easily 
kept  pure  of  admixtures  of  this  kind. 

This  wind-pollinated  condition  of  corn  has  a  great  influ- 
ence on  the  process  of  selection.  In  other  cereals,  whenever 
a  single  head  has  been  selected  in  the  field,  it  is  almost  sure 
to  be  exclusively  self-fertilized  and  its  progeny  will  at  once 
yield  a  pure  and  uniform  race. 

In  corn,  however,  a  selected  ear  will  almost  always  be 
partly  cross-fertilized,  and  probably  by  the  pollen  of  more 
than  one  of  its  neighbors.  If  we  could  eliminate  these  hybrid 
kernels  and  sow  only  the  self-poUinated  seeds,  we  might  ex- 
pect to  get  at  once  a  pure  and  uniform  race,  which  would  need 
only  careful  protection  against  foreign  pollen  during  the  first 
year  of  its  multipUcation.  There  can  be  hardly  any  doubt 
that  this  conclusion,  drawn  from  the  other  cereals,  would 
hold  good  for  corn  also.  At  present,  however,  it  is  impos- 
sible to  distinguish  the  cross-fcrtiUzed  kernels  of  an  ear  from 
the  self-polHnated  seeds,  except  in  such  extreme  cases  as  we 
have  just  alluded  to.  The  only  way  is  to  sow  all  the  seeds, 
and  to  judge  the  plants  when  growing.  In  some  instances 
the  hybrids  may  be  recognized  and  thrown  out  before  tassel- 
ing,  but  ordinarily  they  will  have  to  stand  in  the  field  until 


125 


126 


PLANT-BREEDING 


the  time  of  husking.     Part  of  their  pollen  will  be  carried  to 
the  true  representatives  of  the  chosen  race,  and  repeat  the 

mixture   of  the    charac- 
ters of  the  paternal  and  • 
maternal  strains. 

It  is  easily  seen  that 
in  the  ordinary  process 
of  selection,  the  result  of 
this  open  fertiHzing  con- 
dition must  be  that  the 
choice  is  partly  initial 
and  partly  repeated  or 
continuous.  The  initial 
choice  is  the  main  one  on 
which  almost  all  further 
success  depends,  but  the 
repeated  choice  gradual- 
ly eliminates  the  Ijad 
effects  of  the  una^•oidable 
cross-fertilization  of  the 
^^'■■iiiMt^m  ■       iTffc  ''  ^fiillrt>i     fir^t     chosen    ear.     The 

>.^«/-i^^^. '■  ■■.iJi^  :fla^B?l     initial  choice  corresponds 

to  the  Svalof  method  but 
the  subsequent  repeated 
choice  can  be  compared 
with  the  German  meth- 
od, as  described  in  my 
previous  chapter. 
Or  to  put  it  in  other  words,  the  pedigree  on  the  female 
side  is  pure  and  fully  known,  but  on  the  male  side  it  is  impure 
and  onl}^  vaguely  known  and  must  be  purified  by  repeated 
selections.  Fortunately  in  practice  this  difficulty  is  not  so 
great  as  it  might  seem  to  be,  for  experience  shows  that  as  a 
rule  there  is  a  great  uniformity  in  the  progeny  of  a  single  ear, 


Fig.  38.  The  hand  pollination  of  corn 
in  one  of  the  breeding  blocks  on  the  farms 
of  Funk  Bros.  Seed  Co.,  Bloomington,  111. 


ON   CORN   BREEDING  127 

even  if  this  is  chosen  from  an  ordinary  unbred  variety.  On 
the  other  hand,  as  we  shall  soon  see,  great  care  must  be  taken 
in  order  to  make  sure  that  after  the  first  selection  all  the  sires 
of  the  selected  ears  are  as  superior  plants  as  the  chosen  indiv- 
iduals themselves. 

After  having  discussed  the  effects  of  the  wind-fertiUzing 
conditions  of  corn,  we  have  now  to  consider  the  influence  of 
the  large  size  of  the  ears  and  the  great  number  of  their  kernels. 
This  character  makes  the  comparing  of  corn  ears  far  more 
easy  than  that  of  heads  of  any  other  cereal.  The  qualities 
are  more  easily  appreciated,  and  the  multiplication  being  so 
much  faster,  the  importance  of  the  work  is  greater.  At  the 
time  of  husking,  the  ears  have  to  be  handled  singly  and  this 
will  favor  their  inspection  and  study.  Seed  corn  has  to  be  as 
uniform  as  possiljle,  and  the  easy  inspection  of  the  ears  will 
lead  to  the  elimination  of  all  those  ears  which  do  not  comply 
with  this  condition,  even  in  a  pure  race. 

We  may  assume  that  pure  races  of  corn,  derived  each  from 
a  single  purely  fertilized  ear,  will  show  some  degree  of  varia- 
bility, and  that  this  multiformity  will  strike  us  as  more  im- 
portant than  in  the  case  of  smaller  cereals.  With  the  same 
degree  of  variability  the  smaller  ears  of  wheat,  with  their  mi- 
nute diiferentiating  marks,  will  seem  to  be  more  uniform  than 
a  strain  of  corn,  in  which  the  differences  are  so  much  more 
visible  to  the  eye. 
^  It  is  the  ordinary  or  fluctuating  variability  with  which 

we  have  here  to  deal.  It  embraces  the  elf  ects  of  environmen- 
tal conditions  on  the  plants,  in  the  growing  state  as  well  as 
during  the  ripening  of  the  germ  of  the  seed.  In  the  more 
striking  cases  these  eft'ects  are  well  appreciated  even  by  ordi- 
nar}'  farmers,  and  some  instances  may  be  adduced:  Good 
qualities  may  be  due  to  accidental  advantages,  caused  by 
deficiencies  in  the  neighboiing  plants.  Whenever  the  neigh- 
boring seeds  fail  to  germinate,  or  when  by  some  accident  the 


128  PLANT-BREEDING 

young  plants  are  checked  in  their  development,  the  remain- 
der will  have  more  space,  more  sunlight,  and  more  plant-food 
than  usual.  Everybody  knows  that  ears  which  have  profit- 
ed by  such  exceptional  circumstances,  are  no  true  repre- 
sentatives of  their  race  and  cannot  be  rehed  upon  for  seed 
corn.  Their  excellence  is  not  due  to  inheritance,  they  are 
only  personally  superior  without  promise  of  an  improved 
progeny.  Other  ears  may  fall  back  from  the  average  by 
reason  of  unfavorable  conditions,  without  having  less  value 
as  seed  corn.  It  is  a  most  interesting  fact  that  often  two  ears, 
especially  when  gathered  from  selected  strains,  apparently 
may  be  exactly  similar  and  notwithstanding  this,  give  a  very 
different  progeny  when  tested  separately.  It  shows  that 
there  is  a  kind  of  variability  which  has  no  direct  relation  to 
inheritance,  at  least,  not  in  the  ordinary  sense  of  the  w'ord. 
It  does  not  lead  to  racial  improvement.  Ycry  little  is,  as  yet, 
known  concerning  the  significance  of  the  deviations  from  the 
average  type,  which  purely  bred  strains  of  corn  may  produce 
by  this  unavoidable  and  inexterminable  kind  of  variabiUty. 
We  can  state  only  that  the  characters  of  the  single  cars  of  a 
pure  race  will  differ  somew^hat  from  one  another.  The  char- 
acters are  oscillating  around  the  mean  condition  in  corres- 
pondence to  the  more  or  less  favorable  hfe-concUtions  of  the 
single  plants.  According  to  our  experience  with  other  plants, 
the  deviating  ears  of  a  pure  race  may  possess  the  y)owcr  of 
transmitting  the  good  yielding  quahties  of  the  strain  to  the 
same  degree  as  the  average  specimens.  But,  of  course,  in 
practice,  they  can  hardly  be  reUed  upon  on  account  of  the 
always  possible  contaminations  by  foreign  pollen.  In  all 
cases  where  the  uniformity  of  the  cars  and  the  kernels  is  show- 
ing such  fluctuating  variabiUty  a  choice  of  the  best  ears  will 
have  to  be  made.  But  this  choice  is  made  in  the  interest  of 
a  regular  planting  and  a  normal  stand  and  not  of  a  racial  im- 
provement by  selection.     It  is  difficult  to  appreciate  the  dif- 


129 


I30  PLANT-BREEDING 

ference  between  the  variability  among  tlie  races  and  within 
the  races  themselves,  and  only  a  comparison  with  the  phe- 
nomena observed  in  other  plants  will  lead  to  a  clear  and  use- 
ful distinction. 

The  history  of  the  breeding  of  corn  is  a  very  short  one. 
It  dates  from  the  discovery  of  the  principle  of  single-ear  se- 
lection, ten  years  ago.  The  observation  of  the  individuality 
of  the  progeny  of  one  single  ear  is  the  basis  of  this  method. 
It  enables  us  to  estimate  the  hereditary  value  of  an  ear  by  the 
inspection  of  its  progeny.  It  is  in  full  accord  with  the 
methods  of  Hays  and  Von  Lochow,  who  applied  them  to 
wheat  and  rye,  and  with  the  Svalof  method.  It  is  different 
from  them  only  on  account  of  the  impurity  of  the  fertilization 
of  the  selected  ear,  as  we  have  already  described.  Since 
the  discovery  of  tliis  principle  of  single  ear  selection,  com 
breeding  has  rapidly  developed  and  it  is  now  holding  a 
pre-eminent  place  among  the  methods  of  increasing  the  yield 
of  tills  valuable  crop. 

Previous  to  1897,  Uttle  was  done  in  the  way  of  breeding 
corn  systematically.  It  is  even  as  in  the  case  of  the  Euro- 
pean cereals,  where  but  few  farmers  had  the  idea  of  im- 
proving their  crop  by  selecting  their  seed,  and  became  the 
originators  of  some  few  ameUorated  varieties.  But  they 
did  not  attain  to  any  influence  upon  the  farmers  at  large. 
Working  only  for  the  improvement  of  their  cultures,  they 
failed  to  persuade  others  of  the  vaUdity  and  the  importance 
of  their  views. 

Among  these  men  J.  L.  Learning,  of  Wilmington,  Ohio, 
began  Ms  work  about  1825.  He  simply  selected  the  best 
ears  of  his  field  for  his  seed  corn,  and  in  doing  so  he  soon 
improved  his  strain  of  corn  to  such  a  degree  that  other 
farmers  secured  his  seed-corn  for  their  own  farms,  and  it 
was  soon  imported  into  IlUnois.  There  it  has  since  been 
improved  by  subsequent  repeated  selection,  and  the  T^eaming 


ON   CORN   BREEDING  131 

variety  is  now  considered  one  of  the  best  yielding  sorts  of 
tliis  state.  Half  a  century  afterward,  in  the  year  1875  > 
another  farmer  applied  the  principles  of  cattle-breeding  to 
his  corn.  James  Riley,  of  Thorntown,  Ind.,  selected  seed 
from  the  ordinary  white  corn  of  Indiana  in  order  to  diminish 
the  number  of  barren  stalks  and  of  ears  of  minor  value  in 
his  fields.  By  this  means  he  isolated  a  variety  wliich  he 
called  Boone  County  White  and  which  is  now  the  most 
popular  variety  of  white  corn  in  Indiana  and  IlUnois.  It  is 
one  of  the  best  yi elders. 

It  would  be  superfluous  to  enter  into  more  details.  Some 
crude  attempts  at  selection,  as,  for  instance,  the  separation 
of  kernels  of  cUfferent  color,  have  been  almost  universal. 
Besides  these,  the  comparative  testing  of  different  commer- 
cial varieties  has  long  since  been  the  acknowledged  means 
of  securing  the  types  which  best  responded  to  each  special 
local  demand.  Much  improvement  has  been  obtained  in 
this  way,  but  in  the  long  run  it  has  not  been  adequate  to 
comply  with  the  increasing  necessity  of  keeping  up  with  the 
exigencies  of  consumption  and  industry.  It  is  only  since 
the  discovery  of  the  prominence  of  breeding  from  single  ears 
that  a  start  has  been  made  that  seems  destined  to-  change 
the  whole  aspect  of  agriculture  in  the  corn-breeding  states. 

The  man  who  started  this  new  principle  was  Dr.  Cyril 
G.  Hopkins,  Professor  of  Agronomy  in  the  University  of 
Illinois.  He  proved  the  individuahty  of  the  ears  not  only 
for  the  physical  characteristics  of  their  kernels,  but  also 
for  their  chemical  quaUties.  He  showed  that  corn  may  be 
bred  by  selection  not  only  for  yield,  but  for  special  char- 
acteristics and  value  for  different  industrial  purposes.  He 
succeeded  in  convincing  the  farmers  of  Ilhnois  of  the  great 
possibilities  of  systematic  selection  and  improvement  of 
corn.  The  result  has  been  the  organization  of  a  society 
for  the  purpose  of  putting  corn  selection  on  a  business  basis. 


132  PLANT-BREEDING 

The  Illinois  Seed  Corn  Breeders  Association  was  organized 
in  1900,  and  began  its  work  in  1901.  Soon  afterward, 
similar  associations  were  organized  in  other  corn-breeding 
states,  and  the  systematic  production  of  selected  seed  is 
rapidly  gaining  sympathy  among  the  farmers  throughout  the 
United  States.  In  the  corn  states  it  is,  of  course,  the  dent 
corn  with  its  numerous  varieties  wliich  must  l)e  ameUorated, 
but  in  Connecticut,  Maine,  New  York,  and  other  eastern 
states  the  flint  corns  and  the  sweet  corns  are  equally  in 
need  of  improN'cment.  Farmers  are  now  almost  everywhere 
wilhng  to  pay  higher  prices  for  pedigreed  seed-corn,  although 
these  commonly  average  double  the  value  of  ordinary  seed. 
Corn  breeding  has  become  a  prominent  part  of  the  work  of 
many  of  the  agricultural  experiment  stations,  as  wtII  as  a 
special  business  for  some  large  firms.  Prof.  P.  G.  Holden, 
of  the  Iowa  State  College  of  Agriculture,  at  Ames,  Iowa, 
has  brought  the  work  of  that  station  to  the  front  rank,  and 
the  Funk  Brothers  Seed  Company,  at  Blocmington,  111., 
are  pushing  the  selection  of  corn  as  a  business  enterprise  to 
its  highest  possible  development. 

As  a  rule  seed-corn  has  to  be  purchased  on  the  cob, 
although  the  price  is  often  nearly  double  that  of  shelled  seed- 
corn.  In  Ilhnois  the  price  of  a  bushel,  for  the  best  varie- 
ties, is  in  the  first  case  S3  (70  pounds  of  ears),  and  in  the 
other  case  $2  (56  pounds  of  shelled  corn  per  bushel). 
The  quality  of  the  individual  ears  is  a  criterion  of  the  choice 
condition  of  the  crop  and  a  guarantee  for  the  next  generation, 
but  the  purity  of  shelled  corn  can  never  be  wholly  relied 
upon.  No  seed  should  be  imported  from  distant  locahties, 
except  for  the  purpose  of  experimental  trials.  Ordinary 
unbred  varieties,  which  ronsist  of  mixtures  of  minor  types, 
will,  as  a  rule,  change  during  the  first  years  after  importa- 
tion, some  of  the  constituents  gaining  and  others  losing  in 
their  proportionate  part  of  the  harvest.     Of  course,  such 


Ojn    corn    breeding  133 

changes  can  never  be  accurately  predicted,  and  therefore  the 
vakie  of  an  imported  variety  can  be  determined  only  after 
the  change  has  been  completed.  Northern  varieties  are, 
as  a  rule,  shorter  lived  than  southern  forms,  and  this  is  one 
of  the  main  reasons  why  the  common  behef  of  the  great 
profits  being  secured  by  bringing  in  seed  from  other  locaU- 
ties  is  unfounded.  When  one  goes  south  for  seed-corn,  he 
is  apt  to  get  a  variety  that  will  not  mature  in  his  locaUty, 
and  northern  kinds  will  easily  prove,  on  introduction,  to 
mature  too  early  and  to  yield  a  corresponcHngly  small  crop. 
As  a  rule,  every  degree  north  or  south  of  a  given  locahty 
means  eight  or  ten  days  cUfference  in  the  time  of  ripening. 
No  farmer  can  depend  on  imported  seed  for  his  main  crop. 
He  may  purchase  it  for  his  breeding  plot,  but  he  may  as 
well  select  the  best  ears  from  his  own  fields.  All  trouble 
incident  to  imperfect  adaptation  to  the  local  conchtions  of 
soil  and  climate  can  be  avoided  only  in  this  way. 

I  am  now  coming  to  a  critical  description  of  the  actual 
process  of  corn  breeding  as  it  is  performed  by  the  majority 
of  the  intelligent  farmers  of  the  corn  states.  I  must,  how- 
ever, limit  myself  to  the  main  method,  wlilch,  of  course,  is 
subject  to  many  changes  on  subordinate  points,  according 
to  the  special  demands  of  each  different  locality. 

Three  main  points  in  this  process  have  to  be  considered 
separately : 

First. — The  initial  choice  of  ears  in  the  field. 

Second. — The  comparative  trial  of  the  progeny  of  these 
ears  on  a  breeding  plot,  during  the  summer  subsequent  to 
the  year  of  the  initial  choice. 

Third. — The  continued  selection  and  improvement  of 
the  chosen  strains. 

The  full  appreciation  of  these  three  constituents  of  the 
breeding  process  as  different  processes  will  probably,  some 
day,  prove  to   be  the   most  reliable  basis  for  the   further 


134  PLANT-BREEDING 

development  of  the  practical  methods  of  breeding.  For  this 
reason  I  will  now  discuss  them  as  independent  processes. 

Corn  should  be  selected  in  the  field.  Early  in  the  fall, 
shortly  before  the  time  of  harvesting,  the  farmer  should  go 
through  his  fields  and  mark  the  stalks  of  superior  c|uality. 
Width  of  blade,  indicating  a  rich  foliage  as  the  source  of  the 
organic  constituents  of  the  seeds,  ears  borne  on  shanks 
neither  too  long  nor  too  short,  and  on  an  average  height 
above  the  soil  and  other  essential  quahties  should  decide  the 
choice.  At  the  time  of  husking,  the  ears  of  the  marked 
stalks  are  harvested  separately,  for  the  ultimate  selection. 
Since  it  is  impossible  to  predict  exactly  the  value  of  the 
progeny  from  the  inspection  of  the  parent  plant,  it  is  desirable 
to  collect  as  many  different  types  in  the  field  as  possible. 
Their  real  worth  can  be  determined  only  in  the  next  year. 
But  the  selection  of  that  year  will  evidently  be  limited  by 
the  choice  of  the  first  year,  and  the  wider  this  choice  is,  the 
greater  are  the  chances  of  ultimate  success.  Of  course, 
no  farmer  will  select  plants  or  ears  of  minor  value,  but  he 
should  not  try  to  select  according  to  definite  conceptions 
of  good  rjuahties,  but  simply  try  to  collect  as  many  different 
t}'pes  as  possiljle,  lea\ing  the  decision  concerning  their 
hereditar)'  worth  to  the  next  season.  As  soon  as  he  has  ex- 
hausted the  whole  range  of  the  elementary  constituents  of 
his  varieties,  no  further  field  selection  can  be  of  any  use,  but 
as  long  as  this  limit  is  not  manifestly  reached,  the  fields  con- 
tain possibilities,  which  should  not  be  neglected.  In  ordinary 
cases  it  will  therefore  be  profitable  to  repeat  the  field  selec- 
tion during  some  years. 

Selection  of  corn  is  ^•cry  easy,  when  compared  with  the 
work  connected  with  the  selection  of  other  cereals.  The 
different  marks  of  the  stalks  and  foliage,  of  the  shanks  of 
husks,  of  the  ears  and  the  kernels,  are  easily  appreciated,  and 
their  significance  for  the  value  of  the  new  strains  is  mani- 


135 


136  PLANT-BREEDING 

fest.  Each  farmer  can  gather  the  Knowledge  and  expe- 
rience, which  this  process  rec^uires,  and  a  few  days'  work  in 
a  season  may  secure  great  profits  without  any  notable  outlay. 
Of  course,  the  greatest  profits  will  come  to  those  who  have 
a  taste  for  the  work  and  are  wilUng  to  give  it  the  necessary 
attention.  The  most  successful  farmer  is  the  one  who 
adopts  scientific  as  well  as  practical  business  methods,  and 
who  is  guided  in  his  breeding  w^ork  by  a  thorough  knowledge 
of  the  law^s  of  variabihty.  He  must  be  prepared  to  discern 
the  direct  effects  of  environments  from  the  marks  of  heredi- 
tary quahties.  He  has  to  appreciate  sHght  differences,  in 
the  hope  of  seeing  their  significance  increased  by  the  culture 
of  the  next  year.  By  breeding,  the  yield  per  acre  can  easily 
be  increased  by  five  bushels,  and  it  is  evident  that  tliis  in- 
crease is  pure  profit  to  the  grower. 

The  field  selection  is,  however,  only  preparatory  work. 
The  real  selection  is  obtained  by  the  comparison  of  the  pro- 
geny of  the  chosen  ears.  All  selection  must  be  based  on 
performance,  since  the  aim  of  the  work  is  the  improvement 
of  the  hereditary  ciuahties.  Many  an  ear  has  been  found  of 
excellent  shape  and  size,  with  straight  rows  and  perfect  butt 
and  tip,  with  most  uniform  kernels  of  the  most  desirable 
structure,  but  it  has  been  rejected,  because  it  lacked  the 
power  of  transmitting  these  cjuahties  to  its  progeny.  Often 
of  two  ears  chosen  in  the  field,  and  exactly  similar  in  all 
respects,  the  one  has  given  a  generation  which  yielded  double 
the  harvest  of  the  other.  The  propensity  to  produce  barren 
stalks  cannot  be  judged  by  the  inspection  of  the  ear,  but  it 
becomes  manifest  in  the  generation  cultivated  from  its 
kernels.  ^Nlany  other  instances  could  be  given,  and  all  of 
them  will  point  to  the  same  conclusion,  that  the  hereditary 
quahties  of  an  ear  are  a  character  wliich  demands  special 
investigation.  This  investigation  is  the  separate  culture  and 
exact  comparative  trial  of  the  generation  grown  from  its 


ON  CORN   BREEDING  137 

kernels.  It  is  exactly  the  same  principle  which  now  prevails 
in  the  work  of  the  Swedish  Agricultural  Station  at  Svalof. 

The  comparative  trial  of  the  progeny  of  the  ears  selected 
in  the  field  is  made  on  a  separate  field  plot,  wdiich  is  usually 
called  the  breeding  plot.  Every  corn  grower  should  have 
such  a  breeding  plot.  Here  the  grains  of  each  ear  are  sown 
in  groups,  so  that  it  may  be  easy  to  compare  the  different 
groups  with  one  another.  Two  methods  have  been  pro- 
posed, the  row  system  and  the  plat  system.  In  the  first,  the 
kernels  of  one  ear  are  sown  on  a  row  by  themselves,  the 
second  row  containing  the  progeny  of  a  second  ear  and  so 
on.  By  this  means  the  comparison  of  the  rows  is  the  basis 
of  judging  the  mother  ears.  Experience  has  shown  that  this 
system  is  the  most  convenient,  and  it  is  now  generally  in 
use.  It  is,  however,  exposed  to  the  maximum  degree  of  cross- 
polhnation  and  this  must  manifestly  affect  the  purity  of  its 
harvest.  In  the  system  of  breeding  in  plats,  the  progeny  of 
each  selected  ear  constitutes  a  square  by  itself,  and  thus  at 
least  for  the  central  stalks  a  high  degree  of  pure  fertilization 
by  the  other  members  of  the  same  family  is  insured.  The 
observed  fact  of  the  high  degree  of  individuality  of  each 
family,  derived  from  one  single  ear,  seems  to  point  out  the 
desirability  of  this  plat  system  for  the  first  year  of  trial  on 
the  breeding  plot,  even  if  the  row  system  should  be  kept  as 
the  most  convenient  for  the  subsec[uent  years  of  selection. 
The  experience  gained  at  Svalof  would  justify  the  expectation 
of  a  considerable  shortening  of  the  number  of  years,  re- 
quired to  reach  the  limit  of  possible  purity,  by  the  adoption 
of  the  plat  system  for  the  first  year  of  comparative  trial. 

A  breeding  plot  usually  embraces  about  100  rows,  each 
derived  from  one  mother  ear,  and  in  each  row  about  one 
hundred  hills,  planted  with  three  seeds  each.  At  husking 
time  each  row  is  harvested  separately  and  the  total  weight 
of  its  ears  is  the  main  factor  of  the  comparison,  since  aug- 


138  PLANT-BREEDING 

meriting  the  yield  is  the  most  essential  purpose  of  all  breed- 
ing. The  comparison,  of  course,  suffers  from  the  cross- 
pollinated  condition  of  the  mother  ears,  l)ut,  as  we  have  seen, 
as  a  rule,  not  to  any  noxious  degree,  and  the  plants  grown 
from  such  h}-])rid  kernels  will  probably  be  thrown  out  by 
the  first  selection.  The  plot  should  be  protected  as  effect- 
ively as  possible  from  contamination  by  pollen  from  unbred 
varieties.  As  a  rule,  it  will  hardly  be  possible  to  place  it  on 
good  soil  at  a  sufficient  distance  from  the  remaining  fields, 
and  a  protection  by  hedges  or  timber  will  equally  be  too 
cumbersome  in  ordinary  cases.  The  best  plan  is  to  place 
it  in  the  midst  of  a  large  field  of  a  selected  strain  and  to  sur- 
round it  ])y  three  or  more  rows,  sown  with  the  seeds  of  the 
selected  ears  which  remain  after  the  })reparation  of  the  seed 
corn  for  the  main  rows.  The  first  contrivance  will,  of  course, 
not  be  availaljle  in  the  first  season  after  starting  the  breeding 
plot,  but  from  the  tliird  year  it  will  always  be  practicable. 
In  the  choice  of  the  best  place,  attention  is  to  be  given  to 
the  direction  of  the  prevailing  wdnds,  that  they  may  carry  as 
few  pollen  grains  from  the  adjacent  fields  as  possible.  It 
has  often  been  ascertained  that  pollen  has  drifted  over  a 
quarter  of  a  mile,  and  by  the  planting  of  stray  plants  of  sweet 
corn  and  the  estimate  of  the  number  of  starchy  grains  pro- 
duced on  them,  some  knowledge  concerning  this  transpor- 
tation of  pollen  could  easily  be  secured.  Dr.  Hopkins  has 
pointed  out  the  dangers  of  repeated  self-pollination  in  the 
breeding  plot  and  recommended  the  detasseling  of  alter- 
nate rows  and  the  han'esting  of  the  ears  of  these  rows  only, 
in  order  to  meet  this  difficulty,  but  with  this  question  we  are 
not  here  concerned.  In  the  first  breeding  year  close-pollin- 
ation of  the  progeny  of  the  same  mother  ear  should  be  appre- 
ciated as  a  means  of  shortening  the  period  of  subsequent 
selection;  it  will  probably  prove  harmless  even  if  a  repeated 
close  or  self  fertilization  should  prove  objectionable. 


ON    CORN    BREEDING 


139 


The  best  ears  of  the  breeding  plots  are  divided  into  two 
groups,  the  \ery  best  of  whicli  is  destined  for  the  breeding 
plot  of  next  year,  and  the  other  for  the  multiplying  or  increase 
held.  Here  it  is  cultivated  and  multipHed  in  order  to  vield, 
in  one  year,  all  the  seed  corn  for  the  commercial  fields  of  the 
farm.  By  this  means  well  bred  seed  is  secured  for  the  main 
crop  of  each  year  from  the  breeding  plot  of  two  years  before, 


Fig.  -(.I.  Rows  from  cobs  of  corn  which  have  Ixcu  t-clf-fertilized  and 
from  those  which  have  not  been  self-fertilized.  The  short  rows  being  those 
self-fertilized.  On  the  breeding  blocks  of  Funk  Bros.  Seed  Co.,  IBloom- 
ington,  111. 


either  for  ordinary  purposes  or  eventually  in  order  to  sell  the 
product  of  the  farm  as  pedigreed  seed-corn. 

The  selecting  work  on  the  breeding  plot  can  be  divided 
into  two  parts,  that  before  and  that  after  tasseling.  The 
first  comprises  all  those  characters  which  may  be  judged  on 
the  growing  plants;  the  second  is  mainly  concerned  with  the 
ears  themselves.  The  first  is  accompanied  by  the  extirpa- 
tion or  detasseling  of  all  the  stalks  which  at  that  time  prove 
to  be  of  minor  value  and  so  prevents  them  from  cross-breed- 


140 


PLAXT-HRKKDIXC 


Ing  into  the  remaining  plants.  At  the  time  of  husking,  the 
ears  will  have  been  partly  cross-pollinated,  and  no  account 
can  be  taken  of  this  in  the  selection.  The  judging  and  elim- 
ination of  its  effect  must  be  left  to  the  next  season. 

From  this  discussion  it  is  manifest  that  all  selection 
which  can  possibly  be  performed  before  flowering  should  be 
done  at  that  time  and  be  accompanied  by  the  detasseling  of 


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Fig.  42.     Alternate  detasseled  rows  of  corn,  at  a  lan-r  pcTiuii  ui  giowth 
on  the  breeding-blocks  of  Funk  Bros.  Seed  Co.,  Bloomington,  111. 

the  inferior  stalks.  This  detasseling  is  done  by  pulling  the 
tassels  out  and  is  without  injury  to  the  plant.  It  requires 
going  over  the  field  at  least  three  times,  in  order  to  pull  out 
the  tassels  of  all  the  imperfect  plants,  when  they  are  fully 
developed,  but  before  the  opening  of  the  anthers  and  the 
spreading  of  the  pollen.  No  plants  which  appear  broken, 
dwarfed,  immature,  barren,  or  otherwise  undesirable  should 
be  allowed  to  mature  pollen.  The  occurrence  of  tillers  or 
suckers  and  other  characters  can  be  paid  attention  to.     Rows 


ON    CORN    BREEDING  141 

of  general  inferiorit}-  should  be  dctasselcd  as  a  whole,  since 
in  such  cases  it  is  manifest  that  the  whole  family  has  an 
hereditary  tendency  to  become  imperfect. 

The  main  point,  however,  in  the  selection  before  tassel- 
ing  is  the  occurrence  of  barren  stalks.  Barren  stalks  are 
plants  which  do  not  produce  a  fertile  ear.  As  a  rule  they 
have  imperfect  ears  and  more  or  less  developed  tassels.  It 
is  generally  surmised  that  this  barrenness  is  hereditary, 
although  to  a  large  degree  it  is  dependent  on  cHmatic  con- 
ditions. As  a  matter  of  fact,  seed-corn  wliich  has  been 
fertihzcd  by  pollen  produced  from  barren  stalks  is  liable  to 
give  rise  to  an  increased  number  of  useless  plants.  In  many 
cases  the  number  of  barren  stalks  reached  as  liigh  as  thirty 
per  cent,  and  it  is  e\ident  from  tliis  that  they  are  one  of  the 
greatest  sources  of  loss  in  corn  growing.  They  are  even 
worse  than  a  simple  loss  of  that  amount,  since,  except  for 
detasseling,  they  deteriorate  the  quahty  of  the  neighboring 
ears  as  seed  corn  by  their  pollen.  But  a  Httle  care  in  select- 
ing will  materially  lessen  this  enormous  loss.  The  method 
of  breeding  the  seeds  of  single  ears  in  rows  has  proved  that 
different  degrees  of  barrenness  are  inherent  in  different  fam- 
ilies. Some  ears  produce  more  than  twelve  times  as  many 
barren  stalks  as  others,  and  for  broken  stalks  a  similar  rule 
of  family  indi\iduality  prevails.  Hence  it  is  clear  that  rows 
which  are  marked  in  tliis  deficiency  should  be  detasscled 
as  a  whole,  and  that  their  ears  should  be  excluded  from  the 
ultimate  selection.  Only  strains  with  the  smallest  possible 
propensity  to  barrenness  are  worth  cultivation.  By  follow- 
ing these  rules  the  per  cent  of  barren  stalks  has  been  greatly 
reduced.  For  instance,  in  IlHnois,  on  farms  where  this  num- 
ber reached  as  high  as  about  sixty  per  cent,  it  has  been  re- 
duced by  selection,  in  the  lapse  of  five  years,  to  about  ten  or 
fifteen  per  cent. 

The  high  importance  of  the  combating  of  this  evil  may 


142 


PLANT-BREEDING 


justify  a  discussion  of  this  principle  from  a  scientitic  point 
of  vivw  and  a  few  suggestions  upon  the  great  superiority  of 
the  row  system  of  testing.  The  main  point  is  to  support 
the  view  that  the  detassehng  of  the  barren  stalks  themselves 
is  only  a  very  imperfect  method,  but  that  the  same  treatment 
of  the  whole  rows  is  what  is  absolutely  necessary,  the  pollen 
of  the  normal  plants  of  such  rows  being  as  dangerous  as 
that  of  the  barren  stalks  themselves.  ]\Iy  suggestions  are 
based  partly  on  my  own  experience  with  a  special  kind  of 
barren  stalks,  which  produced  neither  ears  nor  tassels,  and 
partly  on  my  experiments  with  other  kinds  of  monstrosities 
in  other  plants.  For  barrenness  is  to  be  considered  as  a 
monstrosity,  which,  like  all  other  monstrosities,  is  inherent 
in  a  race,  but  is  developed  only  in  a  certain  percentage  of 
its  individuals.  The  same  monstrosity  may  occur  in  some 
races  only  in  a  small  per  cent,  being  found  in  other  strains 
of  the  same  variety  in  as  much  as  30  to  40,  or  even  50  and 
more  per  cent.  Evidently  this  holds  good  for  barrenness  in 
corn,  too,  and  the  families  with  30  to  50  per  cent  are  those 
which  must  l)e  eliminated  by  selection,  while  only  those  with 
a  small  per  cent  may  be  multiplied  until  the  time  that 
strains  will  be  discovered  without  any  propensity  to  this 
deviation.  Ordinary  monstrosities  can  be  propagated,  in 
scientific  experiments,  as  easily  from  the  self-fertilized  seeds 
of  the  completely  normal  individuals  as  from  the  seeds  of 
the  monstrous  plants.  There  is  no  difference  in  the  quan- 
tity of  the  deviating  specimens  of  the  ])rogeny  between  these 
two  sources  of  seed,  the  normal  plants  being  as  liable  to 
give  a  monstrous  progeny  as  the  monsters  themselves. 

Some  instances  may  be  adduced.  Torsions  are  of  quite 
common  occurrence  among  teasels.  I  isolated  a  family 
which  produced  yearly,  during  a  long  series  of  its  biennial 
generations,  from  30  to  45  per  cent  of  twisted  stems.  In 
1900,  I  protected  the  twisted  specimens  from  the  pollen  of  the 


143 


144 


PLANT-BREEDING 


normal  ones  and  these  from  the  pollen  of  the  monstrous  in- 
dividuals and  saved  and  sowed  their  seed  separately.  The 
seed  of  twisted  origin  produced  41  percent  of  abnormal  stalks, 
the  control  seed  giving  37  to  44  per  cent  of  twisted  plants. 


Fig.  44.     Twisted  stems.     A.  Of  a  horsetail    (Equisetum   Telmateja).     B. 
of  the  wild  teasel  {Dipsacus  sylvestris). 


Ribbondike  stems  or  fasciations  are  another  hereditary- 
monstrosity.  In  such  a  race  of  the  hawksbeard  I  isolated  the 
normal  plants  from  the  flattened  stems  and  gathered  the  seed 
separately.     The  first  gave  20  per  cent,  the  latter  20  to  40  per 


Fig.  45.     Sterile  corn,  a  special  form  of  barren  stalks  without  tassel  and 
without  ear.     Originated  in  the  botanical  garden  at  Amsterdam,  1S88. 


145 


146  PLANT-BREEDING 

cent  of  fasciated  stems.  Three  seed-leaves  on  a  germinating 
plant  of  some  dicotyledonous  species  are  inherited  in  the 
same  way  and  so  are  connate  seed  leaves.  Of  the  latter  I 
tried  the  Russian  sunflower,  of  the  former  some  evening  prim- 
roses, and  quite  a  number  of  other  species.  As  a  rule,  the 
seeds  of  normal  plants  which  in  their  youth  had  two  free  seed 
leaves  gave,  after  pure  fertihzation,  the  same  per  cent  of  mon- 
strous seedhngs  as  the  pure  seed  of  the  best  selected  deviating 
specimens.  Hence  we  may  conclude  that  in  races  which  con- 
tain some  kind  of  deviation,  this  is  as  Ukcly  to  be  reproduced 
from  the  seeds  of  the  normal  plants  as  from  those  of  the 
monstrous  specimens.  Applying  tliis  rule  to  barrenness  in 
corn,  we  may  assume  that  the  fertile  stalks  of  rows  which  are 
rich  in  unfertile  plants  are  as  liable  to  deteriorate  the  neigh- 
boring rows  by  their  pollen  as  the  barren  stalks  themselves. 

It  has  been  claimed  that  the  tendency  of  Nature  is  to 
breed  the  barren  stalks  out,  even  without  the  intervention 
of  man.  This  is  evidently  false.  Even  if  the  barren  stalks 
were  as  deficient  in  their  tassels  as  they  are  in  their  ears, 
the  laws  of  nature  would  not  lead  to  any  extirpation.  Year 
after  year  they  would  be  reproduced  by  the  fertile  plants 
wliich  are  derived  from  the  same  mother  ears,  and  on  the 
average,  probably  in  the  same  numbers.  This  conclusion  is 
supported  by  the  evidence  of  my  tasselless  barren  corn, 
which  has  been  reproduced  yearly  from  the  fertile  specimens 
of  the  strain,  during  the  years  of  my  experiment.  All  these 
experimental  facts  go  to  prove  that  the  detassehng  of  barren 
stalks  is  always  only  a  half- measure,  the  rejection  i^f  the 
entire  rows  being  the  only  rehable  process. 

The  main  work  of  the  comparison  of  the  individual  rows 
is  generally  done  at  the  time  of  harvesting  or  shortly  before, 
while  the  plants  are  ripening  in  the  field.  Strong  and  vig- 
orous stalks  of  medium  size,  tapering  gradually  to  the  tassel, 
with  the  ears  at  a  convenient  height  and  having  shanks  of 


ON   CORN   BREEDING  147 

medium  length,  should  be  chosen.  High  ears  tend  to  mature 
later,  too  low  ears  indicate  earhness  in  silking.  Flowering 
before  or  after  the  main  period  of  tassehng,  they  are  cUs- 
posed  to  be  fertihzed  only  incompletely.  In  a  good  stand 
all  the  stalks  should  silk  at  the  same  time.  A  short  shank 
holds  the  ear  too  erect,  while  a  long  shank  allows  it  to  hang 
over  too  far  and  exposes  the  plant  too  much  to  heavy  winds. 
Moreover,  the  long  shanks  arc  inconvenient  in  husking. 
The  suckers,  the  amount  of  leaves,  and  the  growth  of  the 
brace  roots  must  be  considered.  The  time  of  ripening  and 
the  numl)er  of  ears  on  each  stalk  afford  further  differences. 
Plants  which  may  have  profited  by  accidentally  good  condi- 
tions, must  be  excluded  from  the  comparison  since  they  will 
probably  not  be  able  to  transmit  their  exceptional  quahties 
to  their  descendants. 

Records  must  be  made  for  each  indi\-idual  row,  con- 
cerning these  and  other  valuable  characteristics.  The  main 
point,  however,  is  the  total  weight  of  the  ears  of  a  row.  It 
must  be  determined  at  harvesting  time.  It  is  the  one  great 
factor  of  selection,  since  increasing  the  yield  is  the  main 
purpose  of  the  work.  Of  course,  the  rows  have  to  be  of 
ecjual  length,  each  planted  with  the  same  number  of  kernels, 
but  if  this  condition  is  fulfilled,  the  total  weight  of  the  ears 
is  the  primary  factor  in  determining  the  best  rows. 

After  the  husking,  the  characteristics  of  the  ears  and  the 
kernels  should  be  considered.  The  comparative  value  of 
the  kernels  depends  partly  on  the  demands  of  the  planter  or 
planting  machine,  partly  on  their  qualities  for  industrial 
purposes.  No  planter  can  drop  kernels  evenly,  when  they 
are  of  different  sizes  and  shapes.  Experiments  with  mixed 
seed  have  always  given  an  unsatisfactory  stand,  and  only 
perfect  equality  of  kernels  insures  a  perfect  stand.  There- 
fore, the  ears  must  be  judged  after  this  mark  in  the  first 
place.     Tapering  ears  may  have  smaller  kernels  on  the  top 


148  PLANT-BREEDING 

end.  The  rows  must  be  straight  and  uniform,  their  number 
must  be  the  same  over  the  entire  length  of  the  ear.  Devia- 
tions from  these  rules  will  always  result  in  insufficient 
equality  in  the  grains  of  the  seed-corn.  The  butts  and  tips 
of  the  ears  must  be  as  regular  as  possible.  Rough  ears  of 
medium  size  with  a  large  number  of  rows  of  kernels  weigh 
out  the  most  shelled  corn.  The  rows  should  tit  together 
closely  and  leave  no  furrows  between  them.  The  best  kernels 
are  full  and  plump  at  the  tips  next  to  the  cob  and  have  large 
germs,  indicating  high  fcecUng  value.  The  edges  should  be 
almost  straight  in  order  to  fill  out  perfectly  the  available 
space.  The  cob  must  be  of  the  same  color  as  the  kernels, 
especially  in  white  varieties,  since  it  is  impossible  to  remove 
small  particles  of  the  cob,  and  if  the  cob  is  red,  the  meal  will 
be  discolored.  Last,  but  not  least,  the  vitality  of  the  seeds 
must  be  tested.  This  is  a  simple  test  but  of  the  highest 
importance,  which  even  in  ordinary  farming  no  farmer  can 
afford  to  neglect.  (3ut  of  a  hundred  seeds  at  least  93  to  95 
should  germinate.  With  a  lesser  degree  of  vitahty  the 
stand  in  the  field  w^ould  be  very  imperfect,  since  each  failing 
!3eed,  of  course,  causes  the  loss  of  a  stalk  and  an  ear.  Per- 
fect vitahty  insures  a  full  stand  and  manifestly  has  the  great- 
est influence  on  the  yield  of  the  field.  In  many  bulletins 
great  stress  is  laid  on  the  rule,  not  to  spend  time  on  fancy 
points.  These  are  characters  of  the  ears  and  kernels  which 
make  a  deep  impression  on  inspection  but  which  have  no 
relation  to  hereditary  qualities,  or  for  which  at  least  such 
relations  have  as  yet  not  been  proven  beyond  doubt. 

After  all  these  and  many  other  points  have  been  con- 
sidered and  duly  registered,  all  is  prepared  for  the  final  selec- 
tion. Here  the  main  point  is  that  the  rows  should  be  con- 
sidered as  individual  families  and  that  the  best  rows  must  be 
chosen.  No  individual  excellence  of  single  plants  has  any 
hereditary  significance  if  they  are  growing  in  rows  of  less 


A.  B. 

Fig.  46.     Sweet  corn.     A.  With  straight  rows.     B.  With  oblique  rows. 


149 


I50  PLANT-BREEDING 

than  average  value.  The  entire  breeding  plot  has  been 
started  with  the  purpose  of  comparing  the  hereditary  qualities 
of  the  mother  ears,  and  in  estimating  the  result  one  should 
stick  to  this  principle.  Excellent  specimens  in  bad  rows 
may  owe  their  fjuaHties  to  cross-fertilization  of  the  seed  from 
which  they  sprang,  or  to  accidentally  good  environmental 
conditions  during  their  development,  but  in  both  cases  they 
have  to  be  rejected. 

Next  comes  the  question,  how  many  rows  should  be 
selected  for  the  continuance  of  the  breeding  culture?  Of 
course,  only  one  of  them  can  be  the  very  best,  and  if  it  were 
possible  to  select  this  without  mistake,  there  could  not  be 
any  doubt  about  the  vahdity  of  the  principle  of  choosing 
one  single  row.  But  the  experience  of  the  Svalof  Station 
shows  that  even  for  the  ordinary  cereals  such  a  definite 
judgment  can  but  rarely  be  obtained  by  one  year's  trial. 
In  compUance  with  these  considerations,  practical  corn 
breeders  usually  choose  ten  champion  rows  and  start  the 
breeding  plot  of  the  next  year  with  their  seed.  Records  arc 
kept  and  the  origin  of  the  mother  ears  of  each  new  row  can 
be  traced.  By  this  means  a  comparison  of  the  hereditary 
quahties  of  the  grandmother  ears  will  be  possible,  and  this 
will  prove  to  be  very  helpful  in  the  selection  of  the  second 
year.  A  most  complete  analogy  with  the  Svalof  method 
will  thus  lead  to  correspondingly  valuable  results. 

Concerning  continuous  or  repeated  selection,  many  corn 
breeders  in  the  United  States  have  the  same  \iews  as  the 
German  breeders  of  wheat  and  other  cereals.  They  sur- 
mise that  by  careful,  continued  selection,  definite  characters 
can  be  bred  into  the  strains,  according  to  the  wishes  and 
needs  of  the  farmers.  This  is  the  theory  of  slow  improve- 
ment, which  has  obtained  such  a  large  influence  since  Dar- 
win built  upon  it  one  of  the  main  supports  of  his  doctrine 
of  evolution.    In  the  case  of  the  rye  of  Schlanstedt,  described 


ON   CORN   BREEDING  151 

in  our  last  chapter,  I  have  pointed  out  liow  ignorance  of 
the  real  nature  of  the  variability  of  cereals  has  deluded  its 
originator.  It  made  him  assume  that  a  slow  improvement 
was  the  effect  of  his  twenty  years  of  selection,  but  in  reahty 
he  simply  gradually  isolated  by  it  one  of  the  constituents  of 
his  initially  selected  but  mixed  group  of  ears. 

According  to  the  experience  of  the  Svalof  Station,  no 
such  slow  improvement  really  occurs,  and  a  single  choice  of 
an  ear  followed  by  a  separate  culture  of  its  grains  is  always 
sufficient  to  secure  a  pure  and  uniform  strain,  provided  that 
cross-pollinations  do  not  interfere  with  the  result. 

These  principles  must  be  applied  to  corn  breeding  also. 
Any  selected  ear  will  give,  in  its  progeny,  a  pure  and  uni- 
form race  within  the  limits  of  its  fluctuating  variability, 
provided  tliat  it  has  not  been  contaminated  by  crossing. 
Here  we  meet  with  the  main  difference  in  the  breeding  of 
corn  and  of  other  cereals.  With  the  latter  cross-fertilization 
is  an  exception;  with  corn  it  is  the  rule.  This  explains  the 
necessity  of  repeated  selection  of  corn  without  having  to 
assume  the  hypothesis  of  slow  improvement.  Repeated 
flection  i^  the  only  practical  means  of  eliminating  the  effects 
of  previous  crosses.  It  is  only  apparently  a  fixation  of  the 
characters  of  the  young  family;  in  reality  it  is  only  its  puri- 
fying from  vicinistic  impurities.  It  is  enforced  because  of 
the  conviction  of  tlie  detrimental  effects  of  self-fertihzation 
in  corn,  but  if  experience  should  prove  that  one  year's  self- 
fertilization  is  sufficiently  harmless,  the  process  of  corn 
breeding  could  be  shortened  in  tlie  same  way  as  the  Svalof 
method  may  be  considered  as  a  shortening  of  the  older  pro- 
cesses of  breeding  of  cereals.  x'Vn  experimental  test  of  tlie 
value  of  the  Swedish  principles  in  their  application  to  corn 
breeding  would,  no  doubt,  elucidate  many  as  yet  doubtful 
points,  and  probably  lead  to  some  essential  changes  in  the 
practical  work. 


152  PLANT-BREEDING 

Until  now  I  have  almost  exclusively  considered  the 
selection  of  corn  for  yield.  But  since  Hopkins  has  dis- 
covered that  definite  chemical  constituents  of  the  grains 
can  be  improved  also,  the  selection  of  corn  for  special  pur- 
poses has  gained  a  noticeable  significance.  Of  course, 
the  augmentation  of  the  yield  of  shelled  corn  per  acre  will 
always  be  the  main  care  of  the  farmer,  but  the  glucose 
factories  and  the  hominy  mills  will  pay  a  higher  price  for 
corn  that  has  been  improved  according  to  their  special 
industrial  interests. 

In  order  to  understand  how  this  aim  is  reached,  we  must 
first  consider  the  structure  of  the  kernels  and  the  relative 
proportions  of  their  different  parts.  The  kernel  consists  of 
the  germ  or  chip  and  the  endosperm,  enveloped  by  a  very 
thin  covering  called  the  hull.  The  endosperm  consists 
of  the  starchy  and  the  horny  parts;  its  outer  layer,  of  the 
tliickness  of  one  cell,  is  the  glutinous  tissue,  which  may  be 
considered  as  an  inner  covering  and  is  usually  much  tliicker 
than  the  hull.  The  size  of  the  germ  and  the  relative  pro- 
portion of  the  starchy  and  horny  parts  of  the  endosperm 
constitute  most  valuable  varietal  characters.  In  the  starchy 
endosperm  the  tissue  surrounding  the  germ  at  the  tip  end  of 
the  kernel  is  called  the  tip  starch,  the  name  of  crown  starch 
being  given  to  the  starchy  tissue  at  the  upper  end.  These 
parts  are  different  in  their  chemical  constitution.  The  oil 
is  mainly  produced  in  the  germ,  and  the  protein  mainly  in 
the  horny  endosperm.  The  better  developed  these  two 
parts  are  the  richer  the  kernel  will  be  in  oil  or  in  protein. 
The  germ  contains  35  to  40  per  cent  of  oil  or  from  80  to  85 
per  cent  of  the  total  oil  content  of  the  kernel.  The  horny 
endosperm  contains  much  starch  and  about  10  per  cent  of 
protein,  a  figure  which  is  variable  according  to  the  varieties 
tested. 

From  this  description  it  is  easily  seen  that  a  selection 


Fig.  47.  A  kernel  of  corn  cut  longitudinally.  H.  E.  Homy  endosperm. 
M.  E.  Mealy  or  starchy  endosperm.  S.  Scutellum.  G.  G.  Germ.  B. 
The  young  bud  from  which  the  stem  will  develop.  R.  Rootlet.  After 
Frank. 

153 


154  PLANT-BREEDING 

for  oil  content  may  be  made  by  the  choice  of  ears  with  the 
largest  germs,  and  for  protein  b}'  the  selection  of  ears  with  a 
well  developed  horny  endosperm,  or,  since  the  wliite  starch 
is  more  striking  to  the  eye,  with  a  lesser  development  of  this 
tissue,  which  is  poor  in  protein.  This  deduction  has  been 
confirmed  by  the  brilHant  cUscoveries  of  C.  G.  Hopkins,  of 
the  University  of  Illinois,  by  chemical  analysis  as  well  as 
by  direct  breeding  experiments.  In  the  year  i8g6,  he  began 
the  breeding  of  corn  with  the  idea  of  changing  its  chemical 
contents  in  an  experimental  way,  and  selected  seed  of 
white  Illinois  corn  for  four  different  purposes:  High  and 
low  oil  content  and  high  and  low  protein  production.  In 
the  year  1903  he  had  succeeded  in  isolating  four  different 
races,  the  average  ^'alues  of  which  differed  greatly  from 
that  of  the  variety  from  which  he  started.  The  ears  wuth 
the  extreme  percentage  of  these  substances  have  been  picked 
out  by  a  chemical  analysis  of  two  longitudinal  rows  of 
kernels  for  each  ear,  but  their  breeding  ability  has  had  to 
be  studied  in  their  progeny  by  the  row-system,  as  described 
above.  The  result  was  the  isolation  of  high  and  low  oil 
races,  wliich  averaged  6.g6  and  2.62  per  cent,  and  of  high 
and  low  protein  races  containing  14.13  and  6.98  per  cent. 
It  is  evident  that  by  these  most  remarkable  experiments  the 
possibilities  of  the  breeding  of  corn  for  special  purposes  has 
been  demonstrated,  and  the  value  of  this  fact  for  large  in- 
dustrial concerns  can  hardly  be  overestimated. 

For  experimental  tests  and  commercial  purposes  the  dif- 
ferent parts  of  the  kernels  can  be  more  or  less  accurately 
separated.  This  is  done  by  softening  them  in  water  and 
then  passing  them  into  mills.  First  the  hull  is  removed,  the 
germ  is  freed  and  the  starch  body  broken  up.  Water  being 
used,  the  germs,  which  are  lighter  in  weight,  rise  to  the 
surface  and  are  separated.  The  remaining  mass  is  once 
more  milled  or  ground  and  brought  into  a  very  fine  condi- 


In    2 


re    ^ 


c"  s;;- 


iSS 


156  PLANT-BREEDING 

tion.  By  means  of  silk  bolting  cloths  the  hull  or  bean  is 
sifted  out,  and  the  starch,  which  is  heavier  than  the  gluten, 
sinks  to  the  bottom.  Starch  is  the  basis  of  a  large  number 
of  products,  as  for  instance,  glucose,  grape-sugar,  dextrine, 
and  gum.  Among  them,  glucose  is  the  most  important, 
next  to  the  starch  itself.  The  oil  is  isolated  from  the  germs 
by  pressure  after  drying  and  grinding  them  to  a  fine  powder. 
The  residue  constitutes  the  corn  cake  and  corn  meal  which 
is  used  for  feeding  live  stock.  The  oil  itself  is  used  by  paint 
manufacturers,  soap  makers  and  for  the  production  of 
rubber  substitutes,  among  which  the  corn  rubber  or  vul- 
canized corn  oil  is  one  of  the  most  important.  The  hominy 
mills  separate  the  hulls  and  germs  from  the  hominy,  which 
chiefly  consists  of  the  horny  ])art  of  the  kernel,  with  more 
or  less  adhering  starch.  Separated  in  pure  form  and  re- 
duced to  a  coarse  powder,  the  hominy  is  called  grits,  the 
white  starch  being  put  on  the  market  as  corn  Hour  or  break 
flour. 

The  increase  of  protein  is  of  high  value,  inasmuch  as 
corn  is  relatively  deficient  in  this  substance  and  not  a  satis- 
factory food  for  young  animals,  except  when  fed  in  combi- 
nation with  other  nitrogenous  feeding  stuffs.  Protein  is 
several  times  higher  in  price  than  corn  itself,  and  conse- 
quently the  stock  feeders  want  varieties  which  arc  richer  in 
protein  than  the  present  ones.  Any  increase  of  the  protein 
content  by  selection  will  make  corn  more  valuable  as  a  food 
for  live  stock.  It  is  easily  seen  that  even  a  sHght  improvement 
in  tills  direction  would  be  of  tremendous  importance.  And 
in  the  same  way  there  now  exist  markets  for  many  different 
kinds  of  corn.  Besides  the  products  already  named,  whiskey, 
commercial  alcohol,  cellulose  for  coffer  dams  in  battle- 
ships, smokeless  powder,  and  many  other  commocHties  are 
manufactured  from  corn.  But  since  by  far  the  largest 
quantity  of  corn  is  fed  to  cattle  and  other  meat-producmg 


ON   CORN   BREEDING  157 

animals,  the  main  purpose  of  the  farmer  must  always  be, 
next  to  the  increase  of  yield,  to  improve  the  protein  and  the 
oil.  For,  to  put  it  in  a  few  words,  protein  is  a  muscle  form- 
er and  oil  is  the  fat  producing  material.  From  this  point 
of  view  corn  breeding  should  always  embrace  both  (juantity 
and  quality. 

Corn  breeding  is  a  new  industry.  It  is  hardly  older  than 
ten  years.  But  it  has  developed  at  once  on  a  commercial 
scale.  Experience  proves  it  to  be  highly  profitable,  and 
the  conviction  is  rapidly  spreading  that  no  corn  grower 
can  afford  to  be  ignorant  of  its  principles  and  its  results. 


Fig.  49.     Luther  Burbank  of  Santa  Rosa,  Cal. 


IV 

THE  PRODUCTION  OF  HORTICULTURAL 
NOVELTIES  BY  LUTHER  BURBANK 

A.       METHODS    AND    MATERIAL 

The  comircrcial  catalogues  of  the  horticulturists  contain, 
yearly,  a  certain  number  of  novelties.  Some  of  these  are 
introduced  from  foreign  countries,  others  are  due  to  acciden- 
tal sports,  but  many  arc  the  results  of  artificial  improvements. 
They  are  produced  either  by  nurserymen  or  by  private  per- 
sons who  charge  the  seedsmen  with  their  sale.  As  a  rule, 
this  production  of  novelties  is  a  subordinate  matter.  It  is 
very  rare  to  find  a  man  who  devotes  Ms  whole  life  and  all 
his  energies  to  the  introduction  and  production  of  new, 
beautiful  or  useful,  horticultural  plants. 

Such  a  man  is  Luther  Burbank  of  Santa  Rosa  in  CaUfor- 
nia.  He  is  a  nurseryman,  but  has  no  nursery  in  the  orchnary 
sense  of  the  word.  He  is  a  tradesman,  but  sells  nothing 
besides  his  novelties,  and  these  only  to  other  dealers  who  will 
multiply  them  and  offer  them  to  the  general  pubhc.  His 
aim  is  not  the  accumulation  of  wealth,  but  to  contribute  to 
the  welfare  of  other  men  by  giving  them  better  food,  better 
fruits,  and  more  beautiful  flowers.  He  is  especially  interested 
in  the  production  of  cheap  ornamental  plants  for  private 
gardens,  in  order  to  disperse  their  enjoyment  as  widely  as 
possible.  He  is  not  engaged  in  pure  scientific  research,  but 
of  late  he  has  consented  to  have  Ms  methods  and  cultures 
pubhshed,  that  they  may  become  a  guide  for  other  men  in 
their  work  along  the  same  line.  The  Carnegie  Institution 
of  WasMngton  has  accorded  him  an  annual  grant  of  $10,000 
for  ten  years,  thus  enabUng  Mm  to  extend  Ms  cultures  on  as 
large  a  scale  as  is  possible  for  the  work  of  one  man.     More- 

159 


i6o  PLANT-BREEDING 

over,  the  Institution  will  take  in  hand  the  recording  of  the 
history  of  his  experiments  and  thus  create  a  source  of  practi- 
cal and  scientific  information  of  the  highest  importance  upon 
many  c^ucstions  of  plant-breeding. 

Such  a  standard  work  is  the  more  needed,  since  the 
methods  and  results  of  European  horticulturists,  are,  as  a 
rule,  accessible  to  American  breeders  only  with  difficulty. 
Burbank  has  had  to  rediscover  many  of  the  rules  and  prac- 
tices which  in  Europe  were  more  or  less  universally  known. 
His  science  and  methods  arc  his  own  work,  although  in 
comparison  with  those  of  other  horticulturists  they  do  not 
contain  essentially  different  procedures.  It  is  a  most  interest- 
ing study  to  go  into  the  details  of  such  a  comparison,  espec- 
ially since,  by  the  same  principles,  he  has  obtained  such 
strildng  new  results.  If  liis  work  does  not  enlarge  our 
knowledge  of  the  general  rules,  as  it  is  not  intended  to  do, 
it,  at  least,  pro\-idcs  us  ^^ith  such  numerous  illustrations  that 
a  description  of  his  experiments,  even  if  but  brief  and  incom- 
plete, may  be  considered  as  a  renew  of  almost  the  whole 
field  of  horticultural  plant-breeding. 

From  tliis  point  of  \iew  I  shall  now  give  a  survey  of 
Burbank 's  work.  In  doing  so  it  is  not  my  aim  to  recom- 
mend his  fruits  or  Ms  flowers.  They  recommend  them- 
selves, and  their  world-wide  appreciation  gives  the  best 
proof  of  their  high  value.  I  am  concerned  only  with  the 
methodological  side  of  the  work,  and  my  main  aim  is  to  de- 
scribe such  details  as  will  best  contribute  to  the  establishment 
of  the  full  agreement  of  Burbank 's  experience  with  the  agricul- 
tural methods  of  Nilsson  on  the  one  side,  and  with  the  latest 
results  of  biological  investigation  on  the  other. 

Luther  Burbank  was  born  ]\Iarch  7,  1849,  in  Lancaster, 
Mass.  His  father  was  of  English  and  his  mother  of  Scottish 
ancestry.  He  was  reared  on  a  New  England  farm  and 
indulged  in  the  breeding  of  American  grapes  and  of  new 


P    c 


Pd 


X  ^ 


en  3 
o 

P      rf 

•  n 

•  1 


i6i 


i62  PLANT-BREEDING 

potatoes,  which  was  quite  a  common  pursuit  in  ^NEassachu- 
setts  about  the  year  1873.  He  succeeded  in  raising  some 
new  varieties  of  potatoes  in  that  year,  multiplied  them 
during  two  succeeding  summers  and  offered  them  for  sale 
to  the  well  known  seedsmen^  Messrs.  J.  J.  H.  Gregory  & 
Son  at  Marblehead,  ^lass.  They  selected  one  variety 
among  the  three  he  had  offered  and  paid  him  Si 2 5  for  it. 
This  happened  in  the  summer  of  1875,  and  in  September 
of  the  same  year,  Burbank  left  ^Massachusetts  and  settled 
at  Santa  Rosa,  CaUfornia,  partly  on  account  of  his  health, 
partly  on  account  of  the  bright  prospects  which  the  chmate 
of  that  part  of  Cahfornia  offered  him  for  Ms  most  beloved 
occupation,  the  improvement  of  plants.  For  at  Santa  Rosa 
almost  all  the  garden  plants,  which  require  greenhouses  in  the 
eastern  states,  can  be  cultivated  in  the  open,  and  therefore 
on  a  much  larger,  or  even  on  an  almost  unHmited  scale.  As 
an  instance,  I  mention  the  AmarylUs. 

In  the  beginning,  Burbank  rented  a  small  nursery  near 
Santa  Rosa,  and  cultivated  market  flowers  and  small  fruits, 
but  had  to  look  for  work  on  other  farms  also,  in  order  to 
gain  money  enough  for  maintenance.  It  was  only  after  13 
years,  in  1888,  that  he  had  saved  enough  to  buy  liis  present 
farm.  Here  he  organized  a  large  nursery  and  soon  accumu- 
lated a  small  capital,  which  enabled  him  to  sell  out  his  busi- 
ness, in  the  year  1890,  and  to  devote  his  whole  Hfe  to  the 
introduction  and  production  of  novelties.  Three  years 
afterward  (1893)  he  pubhshed  his  first  catalogue  on  "New 
Creations  in  Fruits  and  Flowers,"  which  gained  for  him 
a  world-wide  reputation  and  brought  him  into  connection 
with  almost  all  the  larger  horticultural  firms  of  the  whole 
earth. 

In  1905  he  accepted  the  Carnegie  grant  and  was  appointed 
an  honorary  lecturer  on  plant-breeding  at  the  Leland  Stan- 
ford  Junior  University.     Here  he  deUvers  two  lectures  a 


163 


i64  PLANT-BREEDING 

year  before  a  score  of  advanced  students  and  professors, 
illustrating  his  new  creations  by  means  of  specimens  and 
photograplis,  and  explaining  the  experiments  by  wliich  they 
were  won. 

In  the  meantime,  the  potato  wliich  he  sold  to  Messrs. 
Gregory  had  proved  to  be  a  great  success.  It  had  rapidly 
increased  in  importance  and  supplanted  many  of  the  older 
cultures.  According  to  an  official  statement  of  the  United 
States  Department  of  Agriculture  at  Wasliington  made  a 
few  years  ago,  this  Burbank  potato  is  adding  to  the  agricul- 
tural productivity  of  the  country  an  annual  amount  of 
$17,000,000.  In  the  eastern  states  it  is  cultivated  alongside 
with  other  varieties  and  is  often  indicated  by  local  names 
instead  of  Burbank 's  name.  But  along  the  Pacific  Coast, 
from  Alaska  to  Mexico,  it  is  now  the  standard  of  excellence 
among  potatoes.  In  fact,  it  is  almost  the  only  variety  cul- 
tivated in  Cahfornia,  where  the  culture  of  potatoes  for 
cattle  feeding  or  for  factories  is  of  hardly  any  importance. 
Its  tubers  are  of  a  large  and  (what  is  more  important) 
almost  uniform  size. 

The  evidence  which  is  set  forth  in  this  discussion,  1 
gathered  mainly  during  my  visits  to  the  Santa  Rosa  and 
Sebastopol  farms  of  Burbank,  where  he  was  so  kind  as  to 
explain  his  cultures  to  me  and  to  answer  all  my  cjuestions 
about  them.  I  visited  him  twice  during  the  summer  of 
1904,  and  had  the  privilege  of  a  four-days'  intercourse  with 
him  in  July,  1906.  Of  course,  I  had  prepared  myself  for 
these  \isits  by  studying  the  magazine  articles  on  his  work 
pubHshed  during  the  last  few  years,  and  among  which 
those  of  E.  J.  Wickson  in  Sunset  ^Magazine  may  be  cited  as 
the  most  complete  and  the  most  reUable.  Wherever  pos- 
sible, however,  I  submitted  the  statements  once  more  to  mv 
host,  asking  him  such  questions  about  them  as  would  meet 
the  doubts  which  might  offer  themselves  from  the  standpoint 


o  "•  • 

1-1      1-r     ;-» 


■  n 


i6s 


1 66  PLANT-BREEDING 

of  a  biologist.  As  a  rule,  the  answers  covered  my  wishes 
and  led  to  the  conclusion  that  notwithstanding  the  widely 
divergent,  and  on  some  points  quite  opposite,  methods  the 
main  results  of  practice  and  science  are  the  same. 

In  order  to  understand  the  kind  of  evidence  which  will 
be  discussed  here,  it  is  necessary  to  have  a  clear  idea  of  what 
a  visitor  can  see  on  the  farms.  As  soon  as  Mr.  Burbank  has 
originated  a  new  kind  of  useful  or  ornamental  tree,  flower, 
fruit,  or  vegetable,  he  sells  it  to  one  of  the  great  seedsmen, 
florists,  and  nurserymen  with  whom  he  is  in  constant  relation- 
sliip.  They  take  the  whole  stock,  multiply  it  and  offer  it 
to  the  trade.  They  buy  the  exclusive  right  of  selling  the 
new  variety,  and  nothing  of  it  is  left  on  the  farms  of  Burbank. 
Hence  it  follows  that  a  visitor  cannot  expect  to  have  a  sur- 
vey of  the  achievements  that  have  already  been  made.  There 
is  no  collection  of  these  in  Uving  condition.  One  may 
study  the  commercial  catalogues  of  Burbank  or  inspect  his 
numerous  photographs,  but  the  perfected  varieties  themselves 
are  no  longer  there. 

On  the  other  hand,  the  visitor  to  the  experiment-farms 
will  become  acquainted  with  llie  novelties  destined  for  the 
immediate  future.  Burbank  will  explain  to  him  his  aim  and 
his  hopes  as  well  as  the  methods  by  wliich  he  expects  to 
fulfil  them.  The  future,  however,  is  uncertain,  and  the 
real  value  of  a  novelty  can  be  judged  only  after  some  years 
have  elapsed  after  its  introduction  into  general  culture. 
The  spineless  cactus  opens  the  brightest  prospects  for  the 
cultivation  of  the  arid  deserts,  but  the  trial  to  determine 
whether  it  will  succeed  under  those  unfavorable  conditions 
and  will  reward  the  expenses  of  its  cultivation  must  still  be 
made.  So  it  is  in  many  other  cases  too.  Burbank  himself 
is  the  most  exacting  judge  of  his  productions  and  insists 
that  they  shall  stand  all  tests  of  culture  and  trade  and  shall 
survive  such  exacting  trial  or  perish. 


BURBANK'S   HORTICULTURAL    NOVELTIES     167 

From  this  discussion  it  may  easily  be  seen  that  my  evi- 
dence reUes,  for  a  large  part,  on  experiments  which  are  not 
yet  finished  and  the  ultimate  result  of  which  cannot  yet  be 
estimated.  For  the  description  of  the  methods  used,  this 
is  of  no  importance,  and  in  many  cases  the  older  experiments 
with  their  practical  results  will  have  to  be  alluded  to. 

Burbank's  first  catalogue  was  published  in  1893.  It  is 
now  13  years  old.  The  varieties  described  therein  are,  of 
course,  older,  but  they  are  only  a  small  number  in  ccmiparison 
with  his  present  stock.  The  larger  part  of  liis  experiments  are 
younger,  and  only  a  few  of  his  pedigrees  cover  more  than  ten 
years,  as,  for  instance,  those  of  the  plums. 

A  special  feature  of  Burbank's  work  is  the  large  scale 
on  which  his  selections  are  made.  It  is  evident  that  in  a 
variety  of  mixed  condition,  or  in  the  offspring  of  a  hybrid,  and 
even  in  ordinary  fluctuating  variability  the  chance  of  finding 
some  widely  divergent  individual  increases  with  the  number 
of  the  plants.  In  some  hundred  specimens  a  valuable  sport 
can  hardly  be  expected,  but  among  many  thousands  it  may 
well  occur.  The  result  depends  largely  upon  these  great  num- 
bers. In  one  year  he  burned  up  sixty-five  thousand  two  and 
three  year  old  hybrid  seedling  berry  bushes  in  one  great  bon- 
fire, and  had  fourteen  others  of  similar  size.  He  grafts  his 
hybrid  plums  by  the  hundreds  on  the  same  old  tree,  and  has 
hundreds  of  such  trees,  each  covered  with  the  most  astonish- 
ing variety  of  foliage  and  fruit.  Smaller  species  he  sows  in 
seed-boxes  and  selects  them  before  they  are  planted  out, 
saving,  perhaps,  only  one  in  thousands  or  ten  thousands  of 
seedlings.  Thornless  brambles,  spineless  cacti,  improved 
sweet  grasses  (Anthoxanthum  odoratum),  and  many  others 
I  saw  in  their  wooden  seed-boxes  being  selected  in  this  way. 

The  same  principle  prevails  in  the  selection  of  the  species 
which  are  submitted  to  his  treatment.  Here,  also,  the  result 
depends  chiefly  upon  the  numbers.     He  tries  all  kinds  of 


i68  PLANT-BREEDING 

berries  and  numerous  species  of  flowering  plants.  Some 
of  them  soon  prove  to  be  promising  and  are  chosen,  others 
offer  no  prospects  and  are  rejected.  The  total  number  of 
the  species  he  has  taken  into  his  cultures  amounts  to  2,500. 
The  list  of  the  introductions  of  last  year  shows  500  species, 
mostly  from  South  America  and  Australia.  Formerly  he 
often  made  excursions,  in  order  to  collect  the  most  beautiful 
wild  flowers  or  the  best  berries  of  Northern  Cahfornia,  but 
for  several  years  he  has  had  no  time  to  spare  for  this  work. 
He  has  two  collectors,  who  collect  only  for  him,  and  many 
correspondents  who  send  valuable  bulbs  and  seeds,  from  time 
to  time.  One  of  his  collectors  travels  in  Chile,  the  other  in 
Australia,  preferring  the  regions  in  which  the  cUmate  cor- 
responds best  with  that  of  Santa  Rosa.  The  Australian 
plants  are  usually  sent  to  him  under  their  botanical  names, 
the  South  American  often  without  an}'  names  at  all,  only 
the  date  and  locality  of  collection  being  indicated.  This 
insufficiency  of  denomination  is  of  no  importance  at  all  for 
the  practical  work,  but  often  diminishes  the  scientiffc  value 
of  the  experiment,  as  for  example,  in  the  case  of  the  spineless 
cactus.  The  thornless  species  with  which  he  crossed  the 
edible  varieties  have  been  sent  to  him  from  Mexico  and  else- 
where without  names,  and  they  have  been  eUminated  from 
the  cultures  as  soon  as  the  required  crosses  have  been  made. 
Hence  it  is  evident  that  a  scientific  pedigree  of  his  now  re- 
nowned spineless  and  ediljle  cactus  will  always  remain 
surrounded  with  doubt  as  to  the  initial  ancestry. 

Besides  his  collectors  in  other  countries  and  his  corres- 
pondents widely  scattered  through  the  United  States,  he 
is  constantly  on  the  lookout  for  odd  sorts  of  fruits  or  flowers, 
in  order  to  combine  them  with  the  existing  varieties.  He 
procures  seeds  from  the  nurseries  of  all  countries,  from 
Europe  and  Japan  as  well  as  from  America.  He  brings 
together,  in  each  genus,  as  many  species  as  possible  before 


169 


lyo  PLANT-BREEDING 

starting  his  crosses.  Of  Asclepias  I  noted  about  20  species 
on  a  plot,  of  Brodia^a  four,  of  Rhodanthe,  Schizanthus,  and 
the  fragrant  Tobacco  all  the  best  and  newest  European 
varieties  and  hybrids.  Many  other  instances  will  be  given 
in  the  special  descriptions.  Among  grasses  he  is  now  trying 
species  of  Lolium,  Stipa,  Agrostis,  and  Anthoxanthum, 
partly  for  forage  and  partly  for  lawns.  Of  evening  prim- 
roses he  had  received  a  large  flowered  form  of  the  creeping 
white  CEnothera  albicaulis,  which  he  has  now  selected 
along  with  other  small  and  large  flowered  yellow  primroses. 
Many  wild  species  afford  deviations,  which  are  ordinarily 
considered  as  monstrosities,  but  which  in  his  hand  may  be 
improved  to  yield  valuable  ornamental  plants.  He  showed 
me  a  beautiful  yellow  papaveraceous  plant,  the  Hunnemannia 
fumaria^folia  from  ^Mexico,  which  in  some  specimens 
doubled  its  flowers  on  the  outside  instead  of  within,  in  the 
same  way  as  some  Gloxinias.  Many  other  introduced  de- 
viations and  hundreds  of  beautiful  species  I  saw,  but  there 
is  no  reason  for  mentioning  their  names  here.  \'ery  often 
a  wild  strain  supphes  some  valuable  equality  or  perhaps  only 
the  vigor  of  growth  which  fails  in  its  cultivated  alhes.  Many 
a  weak  race  was  made  strong  by  this  means. 

Among  the  species  and  varieties  introduced  from  foreign 
countries  some  proved  to  surpass  the  corresponding  American 
forms  without  needing  any  improvement.  In  this  way  very 
valuable  contributions  to  American  fruit  culture  have  been 
secured.  In  the  beginning  of  his  work,  a  Japanese  agent 
one  day  sent  him  some  plum  pits.  From  these  he  grew  two 
varieties,  which  he  has  since  introduced  under  the  names  of 
Burbank  and  Satsuma  plums.  The  first  of  them  was  named 
for  him  by  the  United  States  pomologist  at  Washington. 
It  was  exceptionally  suitable  to  American  conditions  and 
has  justified  its  selection  by  its  present  wide  distribution 
and  economic  value.     The  Satsuma  plum  is  now  commonly 


171 


1 7  2  PLANT-BREEDING 

cultivated  in  California  and  is  a  most  delicious  preserve  on 
account  of  its  sweet  flesh  and  small  pits.  The  Burbank 
plum,  on  the  other  hand,  is  one  of  the  best  and  most  popular 
Japanese  plums  throughout  all  the  United  States,  it  is  early 
and  heavy  bearing,  free  from  insects  and  diseases,  and  a 
market  fruit  of  large  size  and  attractive  color. 

Other  species  needed  only  sowing  on  a  large  scale  and  a 
selection  of  the  best  individuals,  and  could  then  be  intro- 
duced without  artificial  improvement.  The  common  French 
prune,  of  which  California  has  produced  one  hundred  and 
fifty  millions  pounds  of  dried  produce  in  a  year,  is  a  small 
fruit  and  late  in  ripening,  although  it  is  rich  in  sugar.  In 
order  to  enlarge  the  size  and  to  change  the  time  of  ripening, 
Burbank  sowed  large  numbers  of  seeds  of  this  French  prune 
d'Agen,  grafted  the  seedlings  on  older  trees  in  order  to  force 
them  to  yield  their  fruits  soon,  and  finally  chose  among  the 
thousands  of  grafts  the  type  which  is  now  known  as  the 
sugar  primes,  a  large  fruit  ripening  a  month  earlier  and 
prolific  in  bearing.  In  the  same  way,  the  crimson  rhubarb, 
or  mammoth  ])ie  plant,  was  secured  which  is  now  grown  on 
a  large  scale  all  around  Los  Angeles,  whence  it  is  shipped, 
during  the  winter  months,  to  the  markets  of  New  York. 
It  is  a  continuous  bearer  throughout  a  large  part  of  the  year 
and  has  a  pecuharly  delicate  flavor.  It  was  sent  to  Santa 
Rosa  by  Messrs.  D.  Hay  and  son,  nurserymen  in  Auckland, 
New  Zealand,  about  fourteen  years  ago.  Burbank  sowed  the 
seeds  on  a  large  scale,  and  selected  the  best  type  for  intro- 
duction as  soon  as  he  perceived  its  excellent  qualities. 
Among  flowers,  the  AustraUan  star  flower  or  everlasting 
(Cephalipterum  Drummondii)  is  now^  being  introduced  after 
only  a  few  years  of  multipUcation  and  selection.  It  is  a 
composite,  and  its  apparent  flowers  are,  in  reahty,  flower 
heads,  the  bright  red  color  of  which  is  due  to  the  bracts  of 
their  invoiucreSj  as  m  other  species  of  everlastings.     It  is 


Fig.  55.     A  hybrid  walnut  {Jiiglans  Calijoniica  nigra),  reaching  double 
the  height  of  ordinary  trees. 


173 


174  PLANT-BREEDING 

recommended  for  millinery  purposes  and  may  supplant  a 
large  part  of  the  trade  in  artificial  flowers.  I  admired,  on 
each  of  my  three  visits,  the  large  beds  full  of  the  shiny  red 
flowers,  and  saw  the  selection  of  the  largest  and  brightest 
specimens  going  on. 

The  main  work  of  Burbank,  however,  consists  in  pro- 
ducing new  varieties  by  crossing.  The  aim  of  crossing  is 
the  combination  of  the  desirable  ([ualities  of  two  or  more 
species  and  varieties  into  one  strain,  and  the  elimination  of 
the  undesirable  characters.  In  the  most  simple  cases  this 
can  be  produced  by  one  cross  and  without  selection;  but, 
ordinarily,  many  crosses  and  the  production  of  a  more  or 
less  chaotic  progeny  are  required,  and  selection  has  to  decide 
what  is  to  hve  and  what  is  to  be  rejected.  It  is  a  well  known 
fact,  discovered  by  Koelreuter  and  Gartner  and  confirmed 
by  numerous  other  scientific  hybridologists,  that  hybrids 
often  surpass  both  their  parents  in  the  vigor  of  their  growth 
and  the  profuseness  of  their  flowering.  Taking  advantage 
of  tliis  rule,  in  more  than  one  instance  Burbank  has  pro- 
duced hybrids  of  extreme  capacities.  The  most  astonishing 
instances  are  afforded  by  his  hybrid  walnuts.  In  the  year 
1891,  he  crossed  the  English  walnut  and  the  Californian 
black  w'alnut  and  afterward  planted  a  row  of  them  along  the 
road  before  his  residence.  At  the  time  of  my  first  visit,  six 
gigantic  trees  were  seen  growing.  They  had  reached  twice 
the  height  and  size  of  ordinary  walnut  trees.  Three  of 
them  he  has  since  been  compelled  to  cut  down,  because  they 
increased  too  rapidly.  This  summer  (1906)  I  saw  the  three 
remaining  specimens,  8c  feet  in  height  and  2  feet  in  diameter. 
He  showed  me  sections  of  the  cut  stems.  Their  wood  was 
of  a  fine  grain,  very  compact  and  of  silky  appearance.  The 
annual  layers  measured  about  5  cm.,  a  most  extraordinary 
thickness.  Fast  growing  trees  are  usuaUy  of  soft  grain,  but 
these  hvbrid  w^alnuts  have  a  wood  as  hard  as  that  of  the 


BURBANK'S   HORTICULTURE 


'ELTIES     175 


ordinary  species.  By  recrossing 
them  the  quahtics  of  the  wood 
have  been  stih  further  improved, 
and  selection  in  tliis  direction 
produces  a  broad  variety  of 
hard  and  soft,  coarse  and  fine, 
plain  and  beautifully  marked, 
straight  and  wavy  grain.  In 
driving  mc  to  his  Sebastopol 
farm,  he  pointed  out  an  enor- 
mous walnut  tree  in  one  of  the 
gardens  along  the  road.  It  far 
surpassed  all  the  surrounding 
trees,  though  many  of  them 
were  older  in  age.  It  is  a  hy- 
brid between  the  native  Cali- 
fornia black  walnut  and  the 
New  England  black  walnut. 
It  is,  next  to  the  redwood  and 
big  trees,  perhaps,  the  largest 
tree  and  the  fastest  grower  I 
ever  saw. 

Another  tree  which  displays 
the  vigor  of  hybrids  is  the 
Wickson  plum.  It  is  a  little 
more  than  ten  years  since  Bur- 
bank  distributed  the  first  grafts 
of  this  variety,  and  it  was  the 
first  of  his  plums  to  make  a 
deep  impression  on  Cahfornian 
fruit  growers.  It  was  produced 
by  crossing  the  above  named 
Burbank  plum  with  the  Kelsev, 
both  parents  being  varieties  of 


Fig.  56.  Extreme  variability 
in  the  size  of  seedlings  of  hybrid 
walnuts  in  the  second  generation. 


176  PLANT-BREEDING 

the  Japanese  Prunus  triflora.  The  flesh  of  the  Burbank 
is  red,  that  of  the  Kelsey  being  dull  pink  and  green. 
The  special  merit  of  the  breeder  lies  in  the  choice  of  the 
parents  from  wliich  to  produce  his  hybrid.  The  Wick- 
son  plum  is,  at  present,  most  largely  grown  in  California 
for  shipping  purposes  on  account  of  its  high  durability. 
It  has  the  unique  heart  shape  of  the  Kelsey,  but  the  flesh 
of  the  Burbank,  a  rich  garnet  and  yellow  color,  a  large  size, 
and  a  perfect  shape.  It  is  very  juicy  and  dchcious,  but  its 
firm  skin  insures  good  shipping  and  keeping  quaUtics.  Its 
first  sales  in  Chicago  made  the  record  for  plum  prices  in  the 
United  States.  It  is  widely  distributed  over  the  world, 
though  somewhat  less  hardy  than  other  varieties.  It  has  the 
best  quahties  of  both  parents  and  in  many  respects  surpasses 
both  of  them.  It  is  one  of  the  best  illustrations  of  what  can 
be  obtained  in  a  single  crossing  by  a  man  who  thoroughly 
knows  all  the  cjuaUties  and  characters  of  liis  trees  and  how 
to  combine  them,  and  who  is  guided  by  this  knowledge  in 
the  choice  of  the  parents  for  his  cross. 

It  is  exceedingly  difficult  to  gain  a  correct  idea  of  the 
influence  which  the  introduction  of  such  novelties  can  have 
over  the  horticulture  of  some  defmite  country  or  state.  The 
Burbank,  Satsuma,  Sugar,  and  Wickson  plums  are  now 
largely  cultivated  in  Cahfornia  as  well  as  elsewhere.  They 
have  partially  supplanted  old  varieties  and  have,  also,  been 
the  means  of  increasing  the  acreage  devoted  to  plum  culture. 
But  it  is  manifest  that  the  change  of  varieties  requires  the 
regrafting  of  the  orchards  and  cannot  be  performed  at  once. 
It  often  requires  ten  years  or  more  to  revolutionize  an  es- 
tablished and  profitable  industry  on  any  large  scale.  It 
takes  some  years  to  prove  the  trustworthiness  of  the  new 
sorts  and  to  convince  the  fruit-growers  of  the  desirability 
of  the  change.  The  production  of  a  new  variety  is  one  great 
step,  but  its  introduction  and  distribution  is  another  equally 


177 


178  PLANT-BREEDING 

important  one.  The  whole  fruit-growing  industry  of 
California  amounts  to  an  aggregate  value  of  about  sixty 
millions  of  dollars  annually,  and  of  this  sum  hardly  one  per 
cent  is  represented  by  the  varieties  imported  or  created  by 
Burbank.  If  we  compare  these  figures  with  those  given  for 
the  importance  of  the  Burbank  potato,  we  find  a  great  differ- 
ence. But  for  a  fair  appreciation  we  must  realize  that  the 
Wickson  plum  is  scarcely  older  than  the  ten  years  recpiired 
for  its  first  wide  distribution  and  that  most  of  the  other  hy- 
brids created  by  Burbank  are  much  younger.  We  must 
leave  it  to  the  future  to  decide  what  will  be  the  real  signifi- 
cance of  the  improvements  in  fruits  and  flowers,  of  which 
this  one  man  has  produced  such  an  astonishing  number  of 
excellences. 

B.  NEW  VARIETIES  OF  ERUITS  AND  FLOWERS 
Since  the  time  of  Darwin,  the  methods  and  achievements 
of  the  breeders  have  played  a  large  part  among  the  argu- 
ments adduced  for  the  support  of  the  doctrine  of  evolution. 
In  a  broad  sense  they  give  us  an  insight  into  the  processes  by 
which  new  forms  are  originated,  and  since  the  general  laws 
of  variabihty  must  be  the  same  for  the  cultivated  condition 
and  for  the  phenomena  of  nature  at  large,  there  can  be  no 
doubt  about  the  general  validity  of  the  argument.  The  ex- 
perience of  the  breeders  teaches  that  new  forms  from  time  to 
time  arise  from  the  existing  ones.  It  gives  a  general  idea 
concerning  the  aflinity  of  the  parent  types  to  their  offspring, 
showing  the  similarity  to  be  very  large  and  the  produced, 
differences  correspondingly  small.  On  the  other  hand  it 
shows  that  by  the  accumulation  of  small  differences,  wider 
cUvergences  may  be  obtained.  Tliis  evidence  led  Darwin  to 
one  of  the  main  propositions  of  his  theory  of  evolution,  viz., 
that  the  larger  groups  in  the  vegetable  Idngdom  have  originat- 
ed in  the  same  wav  in  which  the  smaller  types  are  still  seen 


179 


i8o  PLANT-BREEDING 

to  come  into  existence.  This  proposition  can  be  proved,  and 
in  fact  has  been  proved,  independently  of  the  ([uestion  con- 
cerning the  details  of  that  origin. 

This  broad  principle  of  evolution  by  means  of  natural 
laws  having  been  cstabUshed,  the  question  naturally  arose, 
how  far  the  breeder's  experience  could  be  considered  as  a  re- 
liable guide  in  evolutionary  problems.  On  tliis  point,  how- 
ever, many  difficulties  have  arisen,  all  owing  to  the  simple 
fact  that  practical  breeding  and  scientific  experimenting  are 
things  of  altogether  different  purpose  and  method.  Of  late 
it  has  been  contended  that  the  discussion  of  the  scientific  side 
of  the  question  should  abstain  from  the  use  of  the  breeders' 
results.  There  can  be  no  doubt  that  in  the  end  tliis  will  prove 
the  right  way,  since  only  then  it  will  be  possible  to  submit  all 
arguments  to  the  most  severe  criticism. 

At  present,  however,  the  purely  scientific  investigations 
concerning  variability  and  inheritance  are  only  in  their 
beginning.  Some  fields  have  been  more  or  less  thoroughly 
explored,  and  definite  laws  have  been  cUscovered.  But  the 
more  comphcated  cases  are  as  yet  hardly  accessible  to  our 
analysis,  and  the  breeders'  experience  often  covers  so  long  a 
series  of  years  that  the  science  of  evolution  is  still  quite  inade- 
quate to  ])e  compared  with  it.  ^loreover,  the  practical  re- 
sults contain  so  many  indications  and  hints  for  the  starting 
of  investigations,  and  so  many  details  which  otherwise  could 
easily  be  overlooked,  that  they  are  still  contributing  a  most 
valuable  support  to  evolutionary  science. 

In  estimating  the  value  and  rehabihty  of  the  breeders' 
work  for  theoretical  discussions,  its  methods  and  aims  should 
clearly  be  understood.  The  practical  work  chiefly  consists 
in  the  selection  of  those  specimens  which  arc  most  suitable 
for  the  purpose  under  consideration.  But  selection  recjuires 
material  to  choose  from.  This  material,  in  some  rare  in- 
stances, may  be  directly  afforded  by  nature,  but  in  the  larger 


era" 


W 


i8i 


i82  PLANT-BREEDING 

number  of  cases,  it  must  be  procured  artificially.  The  pro- 
duction and  augmentation  of  variability  is  therefore  to  be 
considered  as  a  second  point  of  almost  equal  importance  to 
the  selection  itself.  It  may  be  either  plain  and  simple  or 
intricate.  In  the  simple  cases  it  is  often  possible  to  trace  the 
whole  line  of  the  work  which  has  led  to  the  ultimate  result. 
In  the  more  intricate  cases,  however,  the  breeders'  purpose 
is  simply  to  increase  the  material  for  their  selection  as  largely 
as  possible.  All  means  conducive  to  tliis  are  combined  and 
the  scientist  finds  himself  at  a  loss  in  trying  to  discern  the  real 
causes  from  amidst  the  chaos. 

For  this  reason,  I  shall  limit  my  present  discussion  to  the 
more  clear  and  simple  instances,  leaving  the  complex  cases 
for  my  next  chapter.  Of  course,  a  sharp  limit  cannot  be  ex- 
pected, and  an  arbitrary  choice  is  unavoidable. 

The  investigations  of  the  past  decades  have  led  to  the  rec- 
ognition of  various  kinds  of  variabiUty,  and  all  further  re- 
search has  to  start  from  these  distinctions.  The  breeders,  on 
the  other  hand,  are  not  concerned  with  these  divisions  and 
simply  consider  the  variabihty  of  their  plants  as  such.  But 
variability  embraces  on  one  side  the  existence  of  a  larger  or 
lesser  range  of  different  types,  and  on  the  other  hand  the 
actual  transformation  of  one  form  into  another.  It  is  evident 
that  a  scientist  wishes  to  know  in  each  case  to  which  of  these 
two  types  an  observed  fact  of  variabihty  belongs,  while  this 
distinction  may  be  indifferent  to  the  practical  man.  In  some 
cases,  however,  it  is  not  at  all  indifferent.  I  mean  those  im- 
provements wMch  have  to  produce  races  that  can  be  multi- 
phed  by  seed.  All  the  varieties  of  cereals,  most  of  the  other 
agricultural  crops,  and  many  kinds  of  garden  plants  belong 
to  this  group.  Here  it  is  manifest  that  only  inheritable  vari- 
ations are  of  consequence,  or  strictly  speaking,  only  those  that 
will  be  repeated  by  generations  raised  from  seeds. 

If,  however,  a  new  type  is  not  intended  to  be  reproduced 


BURBANK'S   HORTICULTURAL    NOVELTIES     183 

by  seed,  the  available  range  of  variability  is  much  larger. 
Such  is,  among  the  larger  crops,  the  case  of  potatoes.  More- 
over it  is  the  rule  for  fruit  trees,  wliich  are  multiplied  l)y  bud- 
ding and  grafting,  and  for  all  the  garden  plants  which  are 
reproduced  from  bulbs,  roots,  layers,  or  cuttings.  In  these 
cases,  inheritance  by  seed  has  manifestly  no  significance  at 
all,  and  all  kinds  of  variations,  which  would  disappear  or  be 
more  or  less  reduced  after  sowing,  here  have  the  same  value 
as  the  strictly  inheritable  characters. 

In  other  words,  the  range  of  variations  is  widened  if  the 
selection  is  hmited  to  varieties  with  vegetative  propagation, 
and  restricted  when  seed  varieties  have  to  be  produced.  It 
is  difficult  to  give  an  idea  of  the  extent  of  this  difference,  but 
it  may  be  stated  here  that  the  best  estimates  lead  to  the  asser- 
tion that  for  vegetative  varieties  selection  finds  a  field  thrice 
as  large  as  for  seed  varieties.  Correspondingly,  the  amehora- 
tions  may  be  thrice  as  important  and  productive  in  the  former 
case  as  in  the  latter.  Hence  it  is  evident  that  whenever  a 
species  can  advantageously  be  multiplied  in  the  vegetative 
way,  its  artificial  varieties  will  manifestly  excel  those  of  ordin- 
ary seed  plants. 

The  most  simple  case  of  producing  new  varieties  is  to 
make  use  of  ordinary  fluctuating  variability.  By  sowing  on 
a  large  scale,  the  extremes  of  tliis  variability  will  easily  be 
obtained,  and  they  will  surpass  the  average  the  more,  the 
larger  the  number  of  seedlings  examined.  One  or  two  of  the 
best  individuals  are  chosen  and  the  rest  destroyed.  The 
chosen  samples  then  become  the  origin  of  a  new  variety  which 
will  remain  constant  as  long  as  it  is  propagated  onlv  in  the 
vegetative  way.  As  a  first  instance,  I  choose  the  loquat  or 
Japanese  quince  (Eryobothrya  japonica).  This  species  has 
small  yellow  fruit  of  an  acid  taste,  almost  filled  with  the 
large  seed,  which  is  covered  with  only  a  tliin  layer  of  fruit 
flesh.     But  it  has  a  peculiar  flavor  found  in  no  other  fruit. 


1 84  PLANT-BREEDING 

Of  this  species,  Burbank  has  sown  thousands  of  seeds  and 
cultivated  the  seedlings  until  they  ripened  their  first  fruits. 
Among  them  he  has  chosen  one  excellent  individual,  which  is 
still  growing  on  Ms  farm  near  Sebastopol.  It  is  a  tree  about 
six  feet  high,  with  wide-spreading  fruit-laden  branches.  Its 
quinces  have  the  same  aroma  as  the  ordinary  loquat  but  are 
much  larger  and  of  an  orange  yellow  color.  Their  seeds  are 
not  larger  than  those  of  the  ordinary  species,  but  the  juicy 
fruit  flesh  is  greatly  developed  in  thickness  and  very  deli- 
cious. These  new  Japanese  quinces  are  considered  as  a 
notable  improvement,  making  one  of  the  finest  dehcacies  for 
the  table.  In  the  same  way,  Burbank  is  trying  to  improve 
the  Cahfornia  currant  (Ribes  sanguineum).  Tliis  species  is 
also  known  as  the  flowering  currant  of  the  Pacific  coast  and  is 
popular  in  European  gardens  as  an  ornamental  spring-flower- 
ing shrub.  It  flowers  profusely  but  is  poor  in  the  ripening  of 
its  fruits.  In  Cahfornia  it  is  abundantly  found  in  the  wild 
state,  and  is  often  densely  covered  with  racemes  of  small  blue 
berries.  It  occurs  in  quite  a  number  of  elementary  types, 
sHghtly  differing  according  to  their  locahties.  Those  of  the 
northern  districts  along  the  Pacific  coast  are  notably  hardier 
in  winter  than  the  more  southern  varieties.  In  such  cases, 
selection  has  to  begin  with  the  choice  of  one  or  two  of  the  ele- 
mentary species,  and  Burbank  preferred  the  hardiest,  v/hich 
he  secured  from  British  Columbia.  In  sowing  the  seed  of 
this  variety  on  a  large  scale,  variations  in  the  size  and  color  of 
the  blossoms,  in  the  number  of  flowers  on  the  raceme,  and 
especially  in  the  development  of  the  fruit,  soon  appeared. 
Among  those  he  chose  the  best  plants  in  dift'erent  directions, 
some  having  long  clusters  of  l)riglit  blossoms,  others  distin- 
guished by  an  increase  of  the  pulp  of  the  berries  or  an  im- 
provement in  the  flavor.  Long  rows  of  shrubs  with  an  almost 
inconceivable  variety  of  fruits  may  now  be  seen  on  his  farm. 
Among  these  a  definite  choice  must  still  be  made  and  proba- 


BURBANK'S   HORTICULTURAL   NOVELTIES     185 

bly  more  than  one  variety  will  recommend  itself  sufficiently 
for  introduction  into  the  market.  Thus  a  new  kind  of  currant 
with  a  liigher  and  more  specific  aroma  will  be  added  to  the 
already  existing  varieties.  It  is,  however,  Burbank's  purpose 
to  submit  these  new  selections  to  the  process  of  hvbridization 
by  crossing  them  w4th  some  other  indigenous  tvpes,  as,  for 
example,  the  glutinous  variety  found  wild  in  the  region  of  San 
Francisco  (Ribes  sanguineum  glutinosum). 

Another  wild  California  fruit  recommends  itself  for  im- 
provement. It  is  the  Elneagnus,  the  pale  yellow  berries  of 
wliich  are  produced  in  such  large  numl^ers  that  the  branches 
are  often  seen  bending  under  their  weight.  They  are  juicy 
enough,  but  the  taste  is  not  that  wliich  is  refjuired  to  make  it 
a  palatable  fruit.  Burbank  has  selected  quite  a  number  of 
types  and  sown  them  on  a  large  scale  in  order  to  gain  a 
marketable  berry.  By  cultivation  the  plants  have  lost  their 
thorns,  as  in  other  instances,  and  the  shape  and  vigor  of  the 
whole  shrub  is  notably  improved.  An  increase  in  fertility  and 
some  amelioration  of  the  taste  has  also  already  been  obtained, 
but  a  large  number  of  liighly  variable  plants  are  still  awaiting 
ultimate  selection. 

Freeing  brambles  of  their  thorns  may  seem  to  be  an  ar- 
duous problem,  Init  reducing  the  thorns  to  practical  harmless- 
ness  is  not  at  all  diflicult,  for  the  prickles  are  variable  in 
number  and  size  like  any  other  character,  and  among  many 
thousands  of  plants  some  will  be  found  very  rich  but  others 
very  poor  in  these  appendages.  Tliis  character  has  the 
great  advantage  of  showing  itself  in  early  youth,  and  so  the 
choice  may  be  made  from  among  the  young  plants  when  still 
in  the  seedling  boxes.  All  the  prickly  ones  are  rejected,  and 
only  the  smooth  ones  planted  out.  It  is  an  astonishing  sight 
to  see  those  long  rows  of  harmless  brambles  awaiting  further 
selection  at  the  time  they  ripen  their  berries. 

The  adduced  instances  may  suffice  to  illustrate  the  prin- 


i86  PLANT-BREEDING 

ciple  of  selection  resting  simply  on  the  ground  of  ordinary 
or  fluctuating  variability.  Its  possibilities,  however,  are 
limited,  and  since  the  breeder  is  always  on  the  lookout  to 
widen  tlie  range  of  his  material,  it  is  but  seldom  that  he  is 
content  with  this  process  of  pure  selection.  In  almost  all 
cases,  he  v/ill  try  to  increase  the  elements  of  his  choice,  and  in 
order  to  do  this,  he  takes  to  the  process  of  hybridization. 

Hybridization,  however,  is  not  always  a  means  of  increas- 
ing variability.  In  some  instances  hybrids  are  as  constant 
and  uniform  as  their  i)arent  species  even  when  propagated 
from  seed.  A  certain  number  of  wild  types  formerly  consid- 
ered and  described  as  pure  species  have  since  been  proved  to 
be  of  hybrid  origin,  the  types  having  been  artificially  produced 
bv  rei)eating  the  assumed  original  cross.  Kerncr  von  Mari- 
laun  has  described  (piite  a  number  of  such  instances,  and 
Janczewsky  and  others  have  produced  hybrids  which  cannot 
be  distinguished  from  real  species  otherwise  than  by  the  his- 
torical record  of  their  birth.  In  such  cases  the  breeder  has 
to  be  content  if  his  hybrid  proves  to  excel  its  parent  species 
in  some  industrial  quality,  but  without  renewed  crosses  Ills 
work  is  Hmited  to  its  production  and  ])ro])agation. 

Some  such  cases  have  occurred  in  Burbank's  work  also. 
As  an  instance  I  will  adduce  the  case  of  a  bramble.  A  cross 
has  been  made  between  the  wild  Californian  dewberry 
(Rubus  CaHfornicus)  and  the  Siberian  raspberry,  or  Rubus 
Sibiricus.  The  first  is  a  small  species  of  bramble  and  the 
second  closely  allied  to  the  common  raspberry.  But  in  both 
the  fruits  are  small  and  worthless.  The  hylirid,  however, 
surpasses  both  its  parents  in  this  important  respect,  having 
large  black  berries,  which  arc  produced  abundantly  and 
ripen  several  weeks  earlier  than  both  parents.  As  the 
first  notable  rmprovement  among  brambles,  it  received  the 
name  of  primus-berry.  Under  this  it  has  found  its  way  into 
the  market.     Other  constant  hybrids  have  since  been  pro- 


BURBANK'S    HORTICULTURAL    NOVELTIES     187 

duced  in  the  same  genus,  among  them  the  phenomenal- 
berry,  which  may  be  described  as  a  gigantic  red  raspberry, 
and  which  is  now  the  most  noted.  It  is  a  hybrid  between 
the  Californian  wild  dewberry  and  the  Cuthbert  raspberry. 
All  of  them  may  be  reproduced  from  seed  as  well  as  in  the 
ordinary  A'egctative  way. 

The  increase  of  variability  which  commonly  is  the  aim 
of  hybridization  may  be  induced  along  definite  or  indefinite 
hues.  In  other  words,  the  combination  of  characters  which 
is  the  cliief  aim  of  crossing,  may  be  so  simple  as  to  be  easily 
calculated  beforehand,  or  it  may  be  so  intricate  as  to  pro- 
duce a  chaos  of  forms  among  which  selection  will  ultimately 
become  the  real  factor  of  improvement.  For  scientific 
purposes,  the  more  simple  cases  are  in  many  respects  the 
most  interesting,  and  for  this  reason  we  shall  now  proceed 
to  the  discussion  of  some  of  them. 

It  is  a  much  discussed  question  whether  new  characters 
may  be  produced  by  crossing.  Of  course,  there  is  no  doubt 
that  new  varieties  and  new  races  may  originate  in  tliis  way, 
but  this  is  not  the  same  point.  It  is  well  known  that  the 
larger  number  of  hybrids  simply  owe  their  character  to  a 
new  combination  of  quahties.  It  is  the  combination  which 
is  new,  not  the  quahties  themselves.  Some  characters  are 
derived  from  one  parent,  others  from  the  other.  Each  of 
them  may  simply  be  inherited  in  the  same  way  as  in  the  case 
of  pure  descent.  But  by  their  new  combinations  they  yield 
varieties  of  higher  practical  value,  and  notable  examples  are 
afforded  in  those  cases  where  one  parent  has  contributed 
vigor  of  growth,  hardiness  in  winter,  resistance  to  disease,  or 
productivity,  and  the  other  bright  flowers,  palatable  fruit, 
or  nutritious  seeds.  For  the  breeder,  such  combinations  of 
characters  have,  of  course,  the  same  value  as  single  favor- 
able marks,  but  from  a  biological  point  of  view  the  two  prin- 
ciples must  be  sharply  distinguished.     The  combination  of 


i88  PLANT-BREEDING 

characters  produces  nothing  really  new,  and  since  this  is 
the  ordinary  case  in  horticultural  crossing,  the  question 
naturally  arises  whether,  besides  them,  from  time  to  time, 
new  elementary  characters  may  arise  by  hybridization. 

Burbank's  experiments  contain  a  number  of  cases  in 
which  the  appearance  of  actual  novelty  is  quite  striking. 
Therefore  1  have  discussed  this  question  with  him  fully,  and 
the  result  is  the  conviction  that  the  novelties  in  question  are 
only  apparent,  and  that  the  real  work  of  the  breeder  is  not 
the  casual  or  accidental  production  of  such,  but  a  systematic 
search  for  rare  and  as  yet  unnoticed,  or  perhaps,  even  for- 
gotten qualities.  It  is  based  on  his  power  to  appreciate  the 
industrial  value  of  characters  which  formerly  had  been 
simply  overlooked  or  considered  of  no  promise  in  a  commer- 
cial direction. 

Before  considering  Burbank's  results  in  tliis  line  of  facts, 
a  few  other  illustrative  examples  may  be  adduced.  One 
or  two  decades  ago,  a  considerable  numl^er  of  varieties  of 
double- flowered  lilacs  had  been  produced  by  Lcmoine  at 
Nancy,  France.  All  of  them  were  hybrids,  and  as  such 
were  very  ornamental  shrubs,  with  large  clusters  of  bright 
flowers,  which  excelled  the  older  kinds  by  flowering  during 
a  noticeably  longer  time.  The  double  flowers,  however, 
were  no  result  of  the  crossing  but  had  been  introduced  as 
such  into  the  group  of  the  ordinary  varieties,  by  crossing 
them  with  an  old  and  forgotten  double-flowered  form,  which 
of  itself  was  hardly  ornamental  on  account  of  its  small  flowers. 
It  was  the  Syringa  azurea  plena,  and  the  real  source  of 
Lemoine's  enormous  success  in  this  case  was  his  idea  of  buy- 
ing a  tree  of  tliis  variety  and  of  starting  a  series  of  crosses 
with  it. 

Another  instance  is  the  seedless  apple,  wliich  is  now  being 
introduced  into  the  trade  as  young  grafted  trees,  wliich  are 
expected  to  exercise  large  influence  on  the  whole  culture  of 


BURBANK'S   HORTICULTURAL   NOVELTIES     189 

apples  as  soon  aa  they  arc  full  grown,  and  shall  have  been 
put  upon  the  market.  The  character  is  nothing  new.  It 
occurs  in  different  varieties  of  apples  and  even  of  pears,  but 
it  seems  to  have  always  been  combined  with  some  defect 
which  made  the  varieties  useless,  or  at  least,  of  inferior 
quality.  Nobody  seems  to  have  suggested  the  idea  of  com- 
bining with  tliis  quahty  the  character  of  our  best  varieties, 
and  so  our  apples  and  pears  are  still  in  possession  of  the 
cores  and  their  seeds.  What  is  new  and  promising  for  this 
most  important  industry  is  the  combination  of  this  rare  and 
almost  forgotten  character  with  the  quahties  of  a  good  and 
marketable  fruit. 

One  of  the  most  interesting  instances  of  this  kind  of 
work  on  Burbank's  farms  is  the  white  blackberry,  a  hybrid 
race  with  abundant  clusters  of  most  dehcious  fruit  of  a  per- 
fect white.  How  can  such  a  simple  mark  as  the  lack  of  the 
black  color  evidently  is,  be  produced  by  crossing?  The 
answer  is  very  simple.  Even  as  in  Europe  a  white  variety 
of  the  raspberry  from  time  to  time  occurs,  so  there  is  found 
in  the  eastern  states,  among  the  cultivated  brambles,  an 
insignificant  variety  with  small  pale  berries.  As  soon  as 
Burbank  had  cUscovered  tliis  fact,  he  secured  some  of  these 
pale  yellow  berries,  introduced  the  type  into  his  culture,  and 
crossed  it  with  the  variety  called  Lawton's  blackberry.  The 
result  was  the  combination  of  the  white  color  with  the  excel- 
lent quahties  of  the  other  parent.  In  a  similar  way,  notable 
quahties  of  rare  or  wild  species  have  often  been  transferred 
by  crossing  on  cultivated  varieties,  thus  giving  rise  to  whole 
groups  of  races  of  a  new  stamp. 

Another  instance  is  the  stoneless  prune,  one  of  the  most 
celebrated  marvels  of  the  Sebastopol  farm.  Only  one  of  its 
varieties  is  ready  for  the  trade,  but  the  remainder  are  still 
in  a  period  of  crossing  and  selection.  A  prolonged  treatment 
must  still  give  them  the  same  size,  fleshiness,  and  flavor  as 


I  go 


PLANT-BREEDING 


other  prunes  have.  The  fruits  we  saw  were  of  a  clear  blue 
color  and  very  attractive,  though  yet  small.  One  may  bite 
completely  through  tlie  middle  of  the  prune,  no  stone  being 
met  with.  Inside  of  the  plum  is  the  seed,  like  an  almond 
in  its  shell,  and  with  a  line  taste  like  that  of  an  almond,  but 
without  any  hard  covering.  It  is  surrounded  only  by  a  pale 
jelly  with  some  stray  remnants  of  hard  stony  material, 
which  do  not  offer  anv  resistance  to  the  teeth  or  to  the  knife. 


Fig.  6c.     The-  improved  stoneless  prune.     The  pit  is  not   surrounded  by 
any  stony  material,  Init  1)\"  a  jelly. 


All  around  the  jell}'  is  the  clear,  greenish,  and  juicy  fruit 
flesh,  exactly  as  in  an  ordinary  plum.  The  amount  of  stony 
remnants  varies  greatly  along  with  the  other  characters. 
Some  hybrids  are  more  stony,  others  less.  The  latter  will  be 
chosen,  in  order  to  be  crossed  with  large,  highly  flavored 
prunes,  so  as  to  obtain  a  superior  quality,  or  they  may  be 
crossed  with  all  other  existing  cultivated  varieties  in  order 
to  transmit  the  lack  of  a  stone  to  all  of  them,  and  so  ulti- 
mately  to  replace  all  the   present  varieties  by  correspond- 


K  V,iEi. 


191 


192  PLANT-BREEDING 

ing  stoneless  ones,  each  of  which  will  be  appropriate  for  the 
the  same  culture  and  use  as  one  of  the  older  types.  Here, 
once  more,  the  question  arose,  can  the  disappearance  of  the 
stone  be  the  result  of  the  hybridization  of  two  or  more  ordi- 
nary varieties?  Burbank's  answer  was  a  negative.  He  had 
followed  fjuite  another  way  in  procuring  this  astonishing 
result.  He  had  noted  that  about  two  centuries  ago,  in 
France,  a  prune  bore  the  name  of  "Prune  sans  noyau." 
It  was  an  indifferent  variety,  more  a  curiosity  than  a 
thing  of  commercial  value,  since  it  produced  only  small 
fruit.  But  Burbank  at  once  realized  all  the  possibihties 
which  this  stoneless  form  offered.  He  was  quite  con\inced 
that  it  needed  only  to  be  crossed  with  the  best  ordinary 
kinds  to  give  a  new  and  most  attractive  fruit.  He  pro- 
cured seed  of  this  long- forgotten  French  prototype  and  sowed 
them  on  his  farm.  By  their  first  fruits  he  satisfied  himself 
of  the  correctness  of  the  description  of  them,  and  of  their 
fitness  for  his  work.  Of  course,  by  one  crossing,  the  chance 
is  not  large  enough  to  get  a  desirable  combination.  Repeated 
crossings  are  rec^uired,  and  each  has  to  be  accompanied  by  a 
selection  of  the  most  promising  specimens.  In  this  way, 
size,  flavor,  and  fleshiness  may  steadily  increase,  while  the 
amount  of  the  remnants  of  the  stone  is  always  kept  as  small 
as  possible. 

A  counterpart  to  the  stoneless  prune,  is  the  spineless 
cactus.  It  belongs  to  the  genus  Opuntia,  some  species  of 
which  are  very  celebrated,  since  they  produce  the  Indian 
figs,  wliich  may  be  seen  on  the  markets  of  New  York  and 
elsewhere  in  the  eastern  states,  where,  notwithstanding  their 
spines,  they  are  highly  appreciated  as  a  dehcacy.  The 
Opuntias  are  desert  plants,  growing  abundantly  and  in  quite 
a  number  of  species  on  the  plains  of  the  semi-arid  regions 
of  the  West.  Their  stems  consist  of  large  flat  pods,  joined 
together  in  the  most  fantastic  manner.     They  are  often  seen 


193 


194  PLANT-BREEDING 

reaching  a  height  of  some  six  feet,  with  numerous  wide- 
spread branches.  Tlieir  fruit  is  rehshed  by  cattle,  being 
juicy  and  nutritious,  and  not  too  spiny.  The  disc-hke  seg- 
ments of  the  stem  also  contain  nutritious  food,  and  this  is 
sometimes  made  use  of,  the  prickles  being  softened  by  cook- 
ing under  the  influence  of  the  juice  from  the  cellular  tissues. 
But  cooking  is  an  expensive  mode  of  preparation,  and  thus 
the  thorns  prevent  the  use  and  culture  of  the  cacti  on  any 
large  scale. 

From  this  discussion  it  is  evident  that  a  spineless  edible 
Opuntia  would  be  a  most  welcome  adcUtion  to  the  agricul- 
ture of  the  semi-arid  West.  It  could  be  cultivated  without 
irrigation  on  the  same  plains  where  the  spiny  forms  now 
occur  in  the  wild  state.  It  would  turn  deserts  into  fertile 
ranches,  admitting  of  cattle  raising,  and  thus  restoring  the 
lands  to  human  industry. 

The  genus  Opuntia  is  very  rich  in  species,  many  of  which 
are  natives  of  Mexico.  Here  some  kinds  occur  which  have 
no  spines  at  all,  and  others  in  which  these  organs  are  only 
partly  developed.  The  spines  of  the  Opuntia  are  of  two 
kinds,  some  being  broader,  smooth  beneath  their  sharp  tips, 
and  of  a  leafy  nature;  others  are  tliin,  covered  all  over  their 
length  by  Uttle  hooks,  and  more  of  the  nature  of  prickles. 
It  is  especially  tliis  latter  kind  whicli  so  often  makes  the 
Indian  figs,  when  not  carefully  peeled,  chsagreeable  for  eat- 
ing. Burbank  transplanted  into  his  garden  as  many  of  these 
deviating  species  as  he  could  lay  hands  on,  and  began  an 
extensive  series  of  crossings.  Their  aim  was  to  combine 
the  absence  of  both  forms  of  spines  with  the  favorable  qual- 
ities of  the  tree-like  kinds  of  the  southern  deserts.  Of  course 
this  could  not  be  reached  by  a  single  cross,  since  numerous 
quahties  have  to  be  considered  before  a  really  productive 
thornless  edible  variety  could  be  secured.  Repeated  crosses 
and  selections  were  rec^uired,  but  the  result  has  ultimately 


195 


196  PLANT-BREEDING 

satisfied  the  liighest  initial  expectations.  Some  large  spec- 
imens of  spineless  Opuntias  may  already  be  seen  on  his  farm. 
They  are  almost  absolutely  smooth,  and  Burbank  dehghts 
in  softly  rubbing  his  cheek  along  them,  in  order  to  give  a 
most  striking  proof  of  their  complete  harmlcssness.  He  is 
now  propagating  them,  and  numerous  young  plants  may  be 
seen  on  his  beds,  wliich  may  some  day  become  the  starting 
point  for  the  desired  new  branch  of  desert  agriculture. 

Some  of  the  hybrids  of  the  stoneless  prunes  I  have 
quoted  as  still  being  in  the  ])ossession  of  small  remnants  of 
the  ancestral  stone.  So  it  is  also  with  the  spineless  cacti. 
Here  and  there  a  stray  spine  may  be  found  on  their  stems, 
but  being  allowed  to  search  for  them,  I  succeeded  only  in 
securing  a  single  one.  If  not  absolutely  absent,  they  are 
at  least,  so  very  rare  as  to  be  practically  innocuous.  Of 
course,  years  will  be  necessary  to  multiply  the  spineless  cactus 
so  as  to  produce  the  enormous  numbers  re([uired  to  replant 
large  parts  of  the  present  deserts.  But  wliile  multiphcation 
may  be  slow  in  the  beginning,  after  some  years  it  will  go  on 
so  rapidly  that  the  practical  result  may  not  be  so  far  off  as  it 
now  seems  to  be.  Burbank  gladly  indulges  in  the  prospects 
which  may  then  be  reahzed,  and  it  seems  hardly  possible  to 
overestimate  the  greatness  of  the  benefit  he  will  have  con- 
ferred upon  mankind. 

As  another  instance,  the  Shasta  daisies  may  be  cited. 
On  meadows,  some  large  flowering  kinds  of  daisies,  or  mar- 
guerites, are  often  seen,  covering  the  green  carpet  like  a  fine 
white  cloth.  They  are  as  bright  as  many  good  garden  flowers, 
but  on  account  of  their  commonness  as  wild  plants,  they 
require  some  improvement  before  being  capable  of  attract- 
ing attention  on  introduction.  They  belong  to  the  genus 
Chrysanthemum,  which  includes  the  Japanese  marigold  and 
other  ornamental  species.  Burbank  has  introduced  into  his 
farm  cultures  a  Japanese  species  closely  related  to  the  mar- 


197 


1 98  PLANT-BREEDING 

guerites  of  the  meadows,  but  surpassing  them  by  the  daz- 
zling whiteness  of  their  flowers  and  some  other  striking  quaH- 
tics.  These  he  has  crossed  with  the  EngHsh  daisy,  which  has 
large  flowers  and  stiff  stems,  and  with  the  American  daisy  of 
the  New  England  states,  which  is  tenacious  of  life  and  hardy 
of  constitution,  but  not  very  white.     By  crossing  these  three, 


Fig.  64.     A  flower-head  of  the  fluted  variety  of  the  Shasta  Daisy. 

he  has  brought  about  a  wondrous  degree  of  variability, 
ranging  from  small,  l)utton-like  flowers  to  others  of  the  size 
of  a  hat.  Selection  thus  being  made  possible  in  different 
directions,  Burbank  chose  that  of  increasing  the  size,  com- 
bining with  it  other  valuable  c|ualities.  The  tall,  stiff  stem 
of  the  English  species,  the  bold  white  flowers  of  the  Japan- 


BURBANK'S    HORTICULTURAL   NOVELTIES     199 

ese  form,  and  the  abundant  bloom  of  the  American  sister 
have  given  the  basis  of  the  combination.  After  this,  selection 
was  made  for  size  and  shape  and  superior  whiteness,  and  a 
variety  was  produced  in  which  the  green  tufts  of  foliage  were 
covered  during'  a  large  part  of  the  spring  and  the  summer 
with  crowded,  bright  white  blossoms.  Tliis  new  and,  on 
account  of  its  easy  propagation,  cheap  garden  flower  received 
the  name  of  Shasta  daisy,  after  the  snowy  mountain  of  that 
name  in  northern  California. 

The  European  marguerites  are  well  known  for  their 
high  degree  of  variability,  and  they  have  transmitted  it  to 
their  hybrid  progeny.  In  combination  with  the  characters 
derived  from  the  other  parents,  this  fact  opens  the  possibility 
of  producing  a  considerable  number  of  secondary  types. 
One  of  them  excels  by  nicely  cup-shaped  flower  heads, 
another  by  tubular  ray-florets.  Some  show  a  tendency  to 
become  double,  and  in  others,  valuable,  or  at  least  curious 
marks,  arc  still  awaiting  selection.  Long  rows  of  these 
bright  blossoms  were  in  full  bloom  at  the  time  of  my  visit, 
and  many  of  them  were  marked  by  httle  ribbons  in  order  to 
save  their  seed  separately  afterwards. 

The  Heuchera  may  be  cited  as  a  parallel  with  the  Shasta 
daisy,  though  their  culture  is  only  in  its  beginning.  The 
garden  species  of  tliis  genus,  Heuchera  sanguinea,  has  long 
but  slight  spikes  of  small  bright  flowers  of  a  blood  red  color. 
It  is  not  a  very  striking  plant,  making  beautiful  tufts  only  by 
very  successful  culture.  It  aft'ords  a  promising  material  for 
amelioration,  but  unfortunately,  its  wild  congeners  are  very 
inconspicuous  plants  with  pale  greenish  or  small  white 
flowers.  Burbank,  however,  discovered,  on  one  of  liis  ex- 
cursions through  the  Californian  forests,  a  local  variety  of 
the  common  Heuchera  micrantha.  This  is  a  nice  little 
plant,  growing  abundantly  along  the  rivulets  in  the  woods. 
He  found  a  plant  with  crisped  leaves  and  decided  to  combine 


200  PLANT-BREEDING 

this  most  beautiful  form  of  the  fohage  with  the  red  blossoms 
of  the  garden  species.  He  transferred  the  plant  to  his  garden, 
crossed  it,  and,  at  the  time  of  my  first  visit,  had  thousands  of 
young  scccUings,  among  which  he  selected  those  which,  by 
the  curled  form  and  brownish  color  of  their  first  leaves, 
already  indicated  the  success  of  his  combination. 

In  the  same  way,  Burbank  has  tried  to  improve  garden 
plants  by  the  introduction  of  some  new  type  and  by  working 
it  "into  the  strain''  as  the  ])hrase  goes.  As  a  last  instance 
his  amelioration  of  the  garden  Canna  may  be  cjuoted.  Every- 
where in  our  gardens  we  may  now  admire,  besides  the  old 
species  and  hybrids  of  Canna,  which  are  still  cultivated  for 
their  large  and  beautiful  foliage,  the  newer  varieties  of  so- 
called  flowering  Cannas.  Their  fohage  is  relatively  low 
but  crowned  with  large  clusters  of  red  and  yellow  flowers. 
They  occur  in  two  types,  the  French  type  or  that  of  Crozy, 
and  the  ItaUan  type  with  its  orchid-shaped  flowers.  Bur- 
bank  has  improved  these  by  the  combination  of  their  quali- 
ties with  those  of  a  native  American  species,  Canna  flaccida. 
Thus  resulted  the  Burbank  Canna,  which  soon  found  its 
way  into  the  gardens  on  account  of  its  giant,  orchid-hke 
flowers.  Its  upper  petals  measure  fully  seven  inches  across 
and  are  of  a  rich  canary  yellow  with  carmine  spots.  A 
second  hybrid  of  the  same  origin  was  the  Tarrytown  Canna, 
notable  for  the  great  abundance  and  richness  in  color  of  its 
flower  spikes. 

Many  other  instances  could  be  adduced,  since  it  is  Bur- 
bank's  custom  to  extend  his  experiments  over  as  many 
species  as  he  can  possibly  bring  together  in  promising 
varieties  or  specimens.  Unfortunately,  the  evidence  which 
is  necessary  to  insure  scientific  value  to  the  practical  ex- 
periments is  not  always  easily  obtained.  From  a  practical 
point  of  \dew,  there  is  no  reason  for  pubhshing  it,  and  when 
it  is  given  in  catalogues  or  references,  this  is  often  done  for 


202  PLANT-BREEDING 

the  purpose  of  illustration  only.  The  fruit-grower  and  the 
amateur  cultivator  of  garden  plants  arc  quite  satisfied  with 
the  visible  qualities  of  their  new  varieties,  and  the  question 
as  to  their  origin  has,  as  a  rule,  but  small  interest  for  them. 
It  is  to  the  personal  kindness  of  Burba nk  that  I  am  indebted 
for  most  of  the  details  conrerning  the  scientific  side  of  his 
cultures,  and,  of  course,  my  visits  were  too  short  to  touch 
upon  all  the  (juestions  exciting  a  similar  interest. 

It  seems  to  me  a  fact  of  high  scientific  significance  that 
combinations  of  characters  can  be  obtained  by  crosses  in 
almost  all  the  arljitrarily  chosen  directions  or  degrees,  but 
that  new  character-units  are  either  never  produced  or  at 
least  so  rarely  tliat  an  artificial  origin  is  hardly  beyond  legiti- 
mate doubt.  Concerning  the  combinations  of  characters, 
the  investigators  of  the  last  decade  have  discovered  dis- 
tinct laws  which,  however,  in  large  part,  are  related  to 
varietal  marks.  Real  specific  differences  must,  of  course, 
also  obey  distinct  laws  in  their  combinations,  and  the  in- 
variability of  some  of  Burbank's  hybrids,  as  for  example  the 
primus-berry,  shows  these  laws  to  be  more  narrowly  cir- 
cumscriljcd  than  is  usually  assumed. 

C.       HYBRIDIZATION    AND    SELECTION 

Apart  from  the  clear  and  simple  cases  we  have  dealt  with 
in  our  last  lecture,  the  ordinary  aim  of  the  hybridizer  is  to 
upset  the  constancy  of  his  plants,  and  to  bring  them  into  a 
state  of  unstable  equilibrium  wliich  in  the  end  will  result  in 
an  extreme  chaos  of  forms.  From  this  chaos,  he  makes 
his  selections,  and  if  they  do  not  at  once  comply  with  his 
wishes,  he  continues  his  crossings  in  order  to  widen  still 
more  liis  range  of  types.  In  doing  so,  he  is  careless  about  the 
real  source  of  the  improvements  he  obtains.  He  knows 
the  origin  of  his  groups  and  strains,  but  rarely  that  of  their 
single  constituents.     Or,  to  put  it  into  a  simple  phrase,  if 


BURBANK'S   HORTICULTURAL   NOVELTIES     203 

his  hybrid  family  is  the  resuU  of  tlie  crosses  of  six  or  eight 
or  perhaps  more  original  species,  he  cIqcs  not  care  whether  a 
given  individual  of  that  family  has  all  those  parents  in  its 
ancestry  or  only  a  few  of  them.  The  visible  features  of 
the  individual  hybrid  often  point  to  ;in  origin  from  definite 
parents  among  the  group.  It  may  have  the  foliage  of  one 
form,  the  branching  of  another,  and  these  combined  with 
the  flowers  or  fruits  or  the  productiveness  of  two  or  more 
others.  Its  pedigree  may  thus  be  guessed  at,  and  for  all 
practical  purposes  this  is  quite  suthcient.  But  in  most  of 
these  cases  a  scientific  treatment  is  excluded,  since  exactly 
that  which  we  should  want  to  pro^■e,  is  simply  assumed  on 
the  ground  of  relatively  loose  probabiUties. 

What  the  breeder  is  very  careful  about  is  the  choice  of 
the  starting  points  for  his  work.  Species,  elementary  species, 
varieties,  individual  excellences,  have  to  be  tested  with  the 
utmost  care  before  being  allowed  an  introduction  into  the 
strain.  For  the  crossing  with  indifferent  types  would  in- 
crease the  work  without  aftording  any  real  chance  of  pro- 
gress, and  species  possessed  of  some  undesirable  character 
might,  of  cours' ,  transmit  this  to  the  hybrids,  as  well  as 
any  favorable  equality.  They  must  be  excluded  at  the  out- 
set, and  this  requisite  is  of  so  essential  a  nature  that  it  may 
be  said  that  half  of  the  ultimate  result  depends  upon  the 
initial  choice  and  only  the  other  half  on  the  success  of  the 
ensuing  hybridizations. 

This  rule  is  often  stated  by  saying  that  half  the  battle  is 
won  by  the  first  selection.  From  it  we  may  deduce  a  con- 
firmation of  our  conclusion  in  the  last  chapter,  viz.,  that  the 
results  of  hybridizations  consist  in  the  combinations  of 
given  characters,  and  not  in  the  accidental  production  of 
new  ones.  All  depends  upon  what  is  already  present, 
since  simply  the  new  grouping  is  the  source  of  the  almost 
inexhaustible  variabiHty. 


204  PLANT-BREEDING 

On  the  farm  at  Sebastopol  I  saw  long  rows  of  Calla,  all 
richly  flowering  and  showing  an  astonishing  amount  of 
variability.  High  and  dwarf  forms  and  all  their  intermed- 
iates, large  and  small  cups,  varying  from  white  to  yellow 
and  not  rarely  spotted,  leaves  of  all  forms  and  color,  some 
hairy  and  some  smooth,  some  of  a  dark  green  and  others 
spotted  or  even  striped  with  white,  more  or  less  purple  and 
brown,  and  with  many  other  differences,  too  many  to  be  here 
summarized.  Add  to  this  various  degrees  of  hardiness  and 
frost  resistance,  a  prolonged  period  of  blooming,  rapid 
propagation  by  means  of  side  shoots,  and  other  cjuaHties 
that  may  cause  the  varieties  to  become  some  day  cjuite 
ordinary  garden  plants  and  you  may  have  some  idea  of  the 
almost  inexhaustible  range  of  variability.  If  we  now  ask 
whence  this  large  group  of  characteristics  comes,  the  answer 
is  readily  given  by  the  history  of  the  culture,  but  whenever 
we  ask  for  the  ancestry  of  one  single  striking  plant,  it  is 
not  historically  known,  but  must  be  derived  from  its  apparent 
affinity  to  some  among  the  ancestors  of  the  whole  family. 

Burbank  began  his  work  on  the  Calla  with  the  ordinary 
cultivated  species,  which  is  almost  everywhere  known  under 
its  names  of  Calla  aethiopica  or  Richardia  africana.  He 
secured  the  commercial  varieties,  including  some  dwarfs  and 
some  spotted  forms,  hybrids  whose  parentage  seems  to  have 
been  forgotten.  From  their  crosses  he  secured  a  fragrant 
variety  with  a  pleasing  perfume.  It  is  of  a  semi-dwarf 
stature  and  is  one  of  the  most  freely-blooming  kinds  within 
the  old  range  of  forms.  Under  the  name  of  "Fragrance" 
it  has  found  general  recognition,  especially  among  eastern 
florists.  The  range  of  possibilities  in  this  group  was,  how- 
ever, very  Hmited  and  seemed  in  the  main  to  be  exhausted. 
Therefore,  Burbank  decided  to  widen  it  by  the  introduction 
of  new  species.  Here  one  of  the  most  striking  features  of 
his  method  may  be  observed.     If  we  consult  the    history  of 


Fig.  67.  The  tiny,  perfectly  formed  Calla,  by  the  side  of  the  one  of  nor- 
mal size,  has  been  bred  downward  to  show  how  plants  mav  be  reduced 
as  well  as  enlarged  in  size.  The  small  one  is  less  than  an  inch  and  a  half 
across. 


205 


2o6  PLANT-BREEDING 

the  most  famous  among  the  older  species  of  garden  flowers 
and  their  hybridizations,  as  for  example  the  Begonia,  the 
Amaryllis,  the  Gladiolus,  and  many  others,  we  find  that 
progress  has,  in  the  main,  been  slow,  advancing  only  by 
more  or  less  accidental  leaps.  These  advances  were  the 
result  of  the  cHscovery  or  introduction  of  new  promising 
species  and  of  their  being  worked  into  the  strain.  They 
often  mark  distinct  periods  in  the  progress  of  these  hybrid 
famihes,  and  not  rarely  they  have  been  achieved  by  different 
breeders.  In  such  cases,  the  history  of  the  \\hole  strain 
may  be  more  or  less  easily  traced.  Opposed  to  these  suc- 
cessive introductions  of  new  species  into  a  h}'brid  family, 
is  Burbank's  principle  to  start  at  the  very  outset  with  as 
many  ])romising  species  as  possil^le,  in  fact  with  all  that  may 
be  available  in  any  nursery  or  botanical  garden,  or  may  be 
collected  in  their  native  haunts  in  any  part  of  the  world. 
The  Callas  give  a  beautiful  instance  of  this  method,  five 
new  tvpes  having  been  added  at  once  to  the  original  stock. 
Of  course,  each  of  them  has  brought  its  peculiar  character 
of  tlowers,  foUage,  and  mode  of  growth,  and  an  almost  endless 
range  of  combinations  must  be  the  result.  Calla  hastata  is 
a  yellow  species  from  the  Congo;  ElUottiana  is  of  a  still 
richer  and  darker  yellow  and  has  spotted  leaves;  Pentlandi 
is  yellow  with  a  dark  purple  spot;  Rehmanni  is  pink  on 
the  outside  and  rose  purple  with  a  crimson  spot  within; 
Nelsoni  is  small,  pale  yellow  and  purple.  All  these  new 
tvpes  have  been  variously  crossed  among  themselves  and 
with  the  old  white  kinds.  Of  course,  the  crosses  were  made 
partly  with  deiinite  combinations  in  view,  and  partly  as 
occasions  were  offered,  and  the  seeds  of  the  crosses  were 
saved  and  sown  in  mixtures.  Each  single  hybrid  of  the  next 
generation  manifestly  had  only  two  parents  and  thus  a  second 
and  even  a  third  season  of  crossing  were  required  to  obtain 
combinations  of  a  higher  rank.     Thus  the  range  of  varia- 


BURBANK'S  HORTICULTURAL   NOVELTIES     207 

bility  has  steadily  been  increasing,  and  it  may  be  doubted 
whether  it  had  already  developed  all  of  its  possibilities  at 
the  time  of  my  visits.  Some  of  the  forms  have  been  put 
upon  the  market,  as  for  example  the  "Lemon  Giant"  which 
is  said  to  be  a  cross  of  the  albo-maculata  and  the  hastata. 
Others  are  still  awaiting  selection  and  recrossing,  but  are 
already  showing  combinations  and  extremes  of  character 
which  are  new  to  the  family.  Among  them  bulbs  of  ten 
inches  across  and  eight  pounds  in  weight,  with  leaves  of 
proportionate  size  and  vigor,  may  be  mentioned.  Each 
year  the  tinest  flowers  and  the  easiest-growing  plants  are 
selected  for  the  new  crosses,  in  order  to  exclude  all  combina- 
tions that  would  not  contribute,  in  the  end,  to  the  main 
purpose,  viz.,  the  production  of  rich  garden  plants  of  easy 
cultivation  and  rapid  propagation. 

The  same  aim  is  pursued  in  the  case  of  most  of  his  other 
attempts  to  improve  flowering  plants.  The  size  and  richness 
of  colors  and  designs  of  the  European  hybrids  of  AmarylHs 
can  hardly  be  improved,  but  they  are  greenhouse  plants, 
requiring  a  number  of  years  for  their  development  and  are 
slow  in  their  propagation.  In  the  beautiful  climate  of  Cal- 
ifornia, they  may,  however,  become  changed  into  garden 
plants  by  first  cultivating  the  best  commercial  hybrids  in  a 
greenhouse,  and  placing  their  pollen  upon  the  ordinary, 
alm.ost  unimproved  varieties  of  the  garden.  By  sowing  the 
crossed  seed  in  the  garden,  the  weakest  and  most  unlikely 
specimens  are  soon  excluded,  and  only  those  remain  for 
repeated  crossing  which  have  inherited  a  sufficient  degree 
of  resistance.  Then  Burbank  worked  for  more  abundant 
bloom,  more  flowers  to  the  scape,  and  more  scapes  from  the 
bulb,  an  earlier  and  more  lasting  blooming  period,  and  lastly, 
for  a  more  rapid  multiplication  in  the  vegetative  way.  I 
inspected  a  bed  of  fme  bulbs  of  Amarylhs  on  the  farm  near 
his  house.     Some  of  them  had  almost  no  side  bulbs  at  all; 


2o8  PLANT-BREEDING 

others  had  produced  some  ten  or  twelve  during  the  summer, 
and  in  the  extreme  instances  this  number  amounted  to  20  to  24 
young  bulbs  on  one  plant.  These  were  marked  for  selection, 
and  their  seed  pods  gave  proof  that  they  had  already  been 
crossed  with  others,  in  order  to  combine  their  abundant  and 
easy  propagation  with  the  hnest  and  most  showy  flowers. 

Similar  results  were  arrived  at  with  the  Gladiolus,  of 
which,  however,  hardy  garden  varieties  had  already  been 
secured  in  Europe.  But  the  stems  were  too  weak,  the  flowers 
too  distant,  the  petals  too  narrow,  and  all  those  deficiencies 
had  to  be  eliminated  by  crossing  with  suitable  parents.  Some 
new  species  were  introduced  from  South  Africa,  and  during 
ten  years,  about  a  million  hybrid  seedlings  w^ere  raised. 
Among  these  quite  a  number  of  new  forms  have  been  chosen, 
being  hardy  plants  for  the  open  air  with  stiff  culms  and 
densely  crowded  spikes  of  large  bright  flowers. 

Experiments  of  this  kind  have  been  quite  numerous. 
Some  are  of  older  date  and  had  already  been  concluded  before 
the  time  of  my  visits.  Others  were  of  more  recent  date  and 
some  only  in  their  beginning.  From  the  long  list  of  species 
treated  in  this  way,  a  few  may  be  chosen  to  give  a  still  better 
idea  of  the  methods  followed.  One  of  his  most  notable 
achievements  is  the  amehoration  of  the  wild  California  tiger 
lily,  Lilium  pardahnum.  This  is  a  species  which  grows 
abundantly  in  many  of  the  redwood  reserves  of  California, 
bearing  its  large  curled  flowers  of  a  fiery  red  on  stems  four 
or  five  feet  high.  It  is  remarka1)le  for  being  very  rich  in 
sub-species  and  varieties,  and  almost  every  locaHty  where  it 
grows  is  said  to  have  its  own  type.  Burbank  collected  as 
many  of  them  as  he  could,  and  crossed  them  with  the  culti- 
vated species  and  hybrids  of  our  gardens.  Hundreds  of 
thousands  of  crossed  seeds  were  produced  and  the  bulbs 
grown  from  them  showed  a  diversity  of  blooms  and  colors 
greatly   exceeding   that   of   the   previous   stock.     Repeated 


BURBANK'S   HORTICULTURAL  NOVELTIES     209 

crosses  had  to  be  made,  and  the  ultimate  result  was  the 
combination  of  the  best  features  of  the  older  garden  liKes 
with  the  typical  form  of  the  California  species.  Many  of 
the  known  lilies  of  the  world  have  brought  their  peculiari- 
ties for  the  enrichment  of  the  native  form,  and  from  half  a 
million  bulbs  some  few  were  in  the  end  selected  as  the  most 
promising  and  were  given  to  the  trade.  All  the  remainder 
of  the  bulbs  were  burned,  with  their  stems  and  flowers,  in 
a  great  bonlire. 

The  clematis  has  produced  a  hybrid  with  bell-shaped 
flowers  of  beautiful  colors.  The  columbines  have  resulted 
in  a  variety  without  spurs.  The  Californian  poppies,  wliich 
are  highly  variable  as  a  wild  species,  have  been  asked  to  widen 
the  range  of  their  flower  colors,  embracing  orange,  white  and 
purple,  and  almost  all  intermediate  shades.  Common  pop- 
pies (Papaver  Rhoeas  and  alhes)  have  produced  not  only  red 
and  white,  striped  and  spotted  varieties,  but  also  a  new  one 
of  a  pale  purpHsh  blue,  wliich,  in  itself,  was  a  quite  insig- 
nificant flower,  but  full  of  promise  of  breaking  up  the  exist- 
ing range  of  colors  and  giving,  by  continued  crosses,  new 
combinations  and  new  shades  outside  of  what  is  already 
known  in  this  group.  The  scented  tobacco  with  its  large 
white  flowers,  which  open  in  the  evening,  has  been  crossed 
with  the  Mexican  Nicotiana  glauca,  a  vigorous  shrub  with 
huge  clusters  of  flowers,  which,  however,  are  of  a  pale  green 
color.  The  combination  had  in  \aew  the  production  of  a 
perennial  and  richly  blooming  variety  with  the  odor  and 
the  bright  flowers  of  the  affinis  parent. 

One  of  the  most  notably  difficult  crosses  is  that  of  the 
common  opium  poppy  with  other  species  of  the  same  genus. 
Ordinarily  the  crosses  are  infertile,  and  success  is  thereby 
excluded.  Burbank  tried  to  cross  it  with  the  Papaver  ori- 
entale,  a  perennial  garden  plant  with  very  large  and  showy 
flowers  of  a  fiery  orange  red.     Like  the  opium  poppy  it  is 


2IO  PLANT-BREEDING 

extremely  rich  in  garden  varieties  and  thus  affords  excellent 
material  for  hybridizations.  The  affinity  between  the  two 
species  is  very  small  and  the  crosses  have  only  succeeded  in 
one  direction.  The  oriental  species  does  not  accept  the 
pollen  of  the  somniferum  even  if  it  is  placed  upon  its  stigma, 
but  remains  wholly  sterile  under  its  influence.  The  recipro- 
cal cross  in  which  the  oriental  is  the  pollen  parent,  produces 
some  few  seeds,  but  from  these  hybrids  arise  with  a  remark- 
able degree  of  variabiHty  in  their  foUage  and  flowers.  The 
hybrids  themselves  are  also  almost  sterile,  some  producing 
no  flowers  at  all;  others  only  small  ovaries  or  miscarried 
ones  reduced  to  a  sharp  point  on  the  top  of  the  flower  stalk. 
They  can,  however,  be  fertiUzed  with  the  pollen  of  the  opium 
poppy,  and  by  doing  so  a  second  generation  of  hybrids  has 
been  produced.  Tliis  generation  gre*v  by  the  side  of  the 
ffrst  one  on  a  bed  of  Burbank's  home  farm,  when  I  visited 
him,  and  was  seen  to  be  extremely  variable  in  its  foliage 
and  in  its  manner  of  growth,  whether  annual  or  perennial. 
Each  individual  was  typical,  having  all  of  its  leaves  of  the 
same  shape,  color,  and  hairiness,  but  among  them  hardly 
any  two  were  ahke.  Selection  must  still  be  made,  and  the 
selected  individuals  must  be  crossed  again  in  order  to  secure 
still  more  beautiful  garden  flowers. 

I  am  now  coming  to  the  description  of  the  most  celebrated 
of  all  Burbank's  crossings,  those  of  the  plums.  In  a  large 
portion  of  the  southern  states,  where  the  European  varieties 
of  plums  had  yielded  only  failures,  notwithstanding  long  and 
careful  attempts,  the  new  hybrids  are  claimed  to  make  plum- 
growing  possible.  In  many  parts  of  Cahfornia  plum  culture 
is  said  to  become  more  profitable  by  the  introduction  of  some 
of  Burbank's  hybrids,  and  a  new  epoch  of  fruit-tree  growing 
has  thereby  been  opened.  Hardiness  and  productiveness 
are  the  main  features  1)y  which  these  results  have  been 
secured,  and  they  themselves  were  obtained  by  the  combina- 


BURBANK'S   HORTICULTURAL   NOVELTIES     211 

tion  of  the  characters  of  Japanese  and  native  American 
species,  with  the  flavor  and  fleshiness  of  the  older  cifltivated 
sorts.  Some  of  his  best  hybrid  and  introduced  varieties  may 
be  named  and  briefly  described,  according  to  the  claims  of 
their  originator.  "Abundance"  and  "Burbank"  may  thrive 
almost  everywhere.  They  are  capable  of  resisting  frost 
during  the  period  of  blossoming.  The  "Burbank"  is  said 
to  supplant  the  older  varieties  over  large  regions  and  may 
even  be  cultivated  in  districts  where  plum  culture  was  for- 
merly impossible.  It  has  been  exported  to  South  Africa, 
Australia,  and  New  Zealand,  and  many  thousands  have  been 
planted  in  these  distant  countries.  It  has  proved  to  be  the 
most  reliable  plum,  as  well  for  household  purposes  as  for 
canning  and  sliipping.  "Sweet  Brotan"  is  another  success- 
ful hybrid,  and  "Satsuma, "  an  introduced  variety  miscarries 
in  some  districts,  but  yields  a  large  harvest  in  others.  About 
twelve  years  ago,  the  giant  prune  was  introduced.  Others 
arc  younger,  and  almost  every  year  some  new  ones  are  placed 
on  the  market.  Their  total  number  now  exceeds  a  dozen. 
Of  the  youngest  varieties  the  fruits  are  not  yet  on  the  market, 
and  only  cuttings  or  young  trees  are  for  sale.  In  some  cases 
companies  have  been  organized  with  the  aim  of  propagating 
and  multiplying  one  of  Burbank's  hybrids,  in  order  to  dis- 
tribute thousands  of  trees  at  the  first  moment  of  introduction 
to  the  public.  The  Maynard  plum  may  be  cited  as  an 
instance. 

Ordinarily,  Burbank  sells  the  whole  variety  and  leaves 
the  propagation  and  sale  to  other  men.  The  result  is,  that 
of  his  previous  hybrids,  nothing  is  now  to  be  seen  on  his 
farm.  The  visitor  sees  hundreds  of  trees,  each  grafted  with 
from  twenty  to  forty  or  often  more  hybrids,  all  of  which  are 
awaiting  trial  and  selection.  ?Iere  the  prunes  of  the  future 
are  growing,  but  of  course  they  are  rare  instances  among 
the  thousands  of  good  and  palatable  fruits  that  will  have  to 


212  PLANT-BREEDING 

be  rejected.  The  casual  inspector  cannot  discern  them,  and 
moreover  he  is  simply  bewildered  by  the  profusion  of  lus- 
cious fruits  which  arc  tempting  his  eyes  and  palate  on  all 
sides. 

Among  the  American  species  of  the  large  plum  genus,  the 
beach  plum  or  Prunus  maritima  plays  a  prominent  part  in 
Burbank's  crossings  on  account  of  the  small  demands  it  makes 
on  soil  and  water.  It  is  one  of  the  most  common  shrubs 
along  the  eastern  shores,  growing  everywhere  on  the  coast 
or  along  the  larger  rivers,  in  dense  l)ushes.  It  is  very  pro- 
ductive and  is  satisfied  with  almost  any  life  conditions.  It 
thrives  as  abundantly  on  dry  and  sandy  plains  as  where  the 
s:)il  is  covered  by  salt  or  fresh  water  during  part  of  the  year. 
It  abounds  in  varieties  having  red  or  blue  or  yellow  prunes, 
sometimes  large  and  sometimes  small,  ripening  early  in  some 
locahties  and  late  in  others,  affording  thereby  a  rich  material 
for  selection  and  hyljridization.  The  prunes  are  often  as 
small  as  huckleberries  and  are  gathered  only  for  preserving 
purposes,  but  it  blooms  a  month  after  most  of  the  other 
species  and  is  thereby  almost  free  from  the  danger  of  having 
its  blossoms  destroyed  by  frost  while  it  proceeds  with  the 
ripening  of  its  fruit  until  late  in  the  fall. 

All  these  notable  qualities  Burbank  has  tried  to  transmit 
to  his  hybrids,  comljining  them  witli  the  usual  reciuirements 
of  palatable  plums.  By  successive  crosses  and  correspond- 
ing selections,  the  bush  form  of  the  beach  plum  has  been 
eliminated  from  the  hybrid  strains,  upright  trees  having 
been  preferred  for  the  further  crosses.  Stones  as  small  as 
those  of  the  cherry,  in  plums  of  full  size  are  another  result 
of  these  combinations.  The  first  generation  of  the  original 
crosses  were,  of  course,  only  of  relative  value,  but  by  re- 
crossing  them  with  as  many  varieties  and  hybrids  as  were 
available,  an  extremely  rich  material  for  selection  has  been 
secured. 


BURBANK'S   HORTICULTURAL    NOVELTIES     213 

In  some  cases,  the  history  of  the  succeeding  crosses  may 
still  be  traced,  although  of  course  the  selection  has  steadily 
eliminated  some  characters  and  augmented  others.  But 
wherever  the  pedigree  is  historically  known,  the  explanation 
of  the  different  characters  of  a  hybrid  and  their  reduction 
to  those  of  the  single  parental  types  is,  of  course,  more  reliable 
than  in  the  ordinary  cases.  As  an  illustration,  Burbank  has 
described  the  pedigree  of  his  x\lhambra  plum.  It  is  a  com- 
bination of  seven  distinct  parents,  some  of  which  are  of 
American,  some  of  Japanese  and  others  of  European  origin. 
Among  the  latter  some  are  probably  the  offspring  of  old  and 
long-forgotten  crosses,  thus  making  the  pedigree  still  more 
comphcated.  Each  generation  requires  about  three  years, 
the  seedhngs  being  grafted  in  their  first  summer  on  old  trees 
and  thereby  being  brought  to  blossom  at  a  very  early  period- 
of  their  hfe.  The  whole  pecUgrec  includes,  by  this  manage- 
ment, only  thirteen  years.  The  initial  cross  was  made 
between  the  Kelsey  plum  and  Prunus  Pissardi,  an  ornamen- 
tal tree  with  a  dark  purpHsh  foliage  but  without  edible  fruit. 
The  offspring  of  this  cross  was  fertilized  with  the  pollen  of 
the  flowers  of  the  French  prune,  and  the  threefold  hybrid 
thus  improved  w^as  destined  for  still  further  combinations. 
For  these,  in  the  meantime,  hybrids  had  been  prepared  in 
order  to  bring  the  desirable  characters  of  two  new  forms  into 
the  strain  by  means  of  a  single  cross.  First  a  hybrid  of 
Simoni  and  triflora  was  used,  and  the  offspring  obtained 
in  this  way  was  fertihzed  with  the  pollen  of  Americana  x 
nigra,  bringing  up  the  total  number  of  the  constituents 
to  seven.  Of  course,  the  offspring  of  this  last  cross  was 
utterly  variable  and  among  it  the  x\lhambra  was  chosen  as 
the  best. 

Summing  up  the  main  Hncs  of  this  historical  sketch,  we 
may  put  them  into  the  following  pedigree : 


214  PLANT-BREEDING 

Kelsey ......  x Pissardi 

a .....  X  French  prune 

Simoni  x  tritlora x b 

c X  Americana  x  nigra 

Alhambra. 

It  seems  hardly  necessary  to  point  out  that  the  Alhambra 
has  neither  been  the  only  result  of  this  pedigree  nor  that  the 
crosses  in  its  ancestral  Une  have  been  the  only  ones  performed. 
Quite  on  the  contrary,  this  pedigree  is  only  to  be  considered 
as  one  of  the  hundred  or  perhaps  thousands  of  diverging 
Hnes  by  wliich  the  main  types  and  their  numerous  subordinate 
varieties  have  been  combined  with  one  another.  The  re- 
sult has  been  an  utter  chaos  of  mainly  excellent  kinds  of 
prunes  such  as  it  was  at  the  time  of  my  visits.  Of  some  of 
them  the  pedigree  could  be  traced,  but  there  were  many  of 
doubtful  superiority,  for  wliich  it  would  not  be  worth  while 
to  keep  the  historical  record. 

The  selection,  of  course,  must  be  performed  chiefly  dur- 
ing the  few  summer  weeks  when  the  branches  of  the  grafted 
trees  are  loaded  with  ripe  fruits.  It  is  a  most  curious  sight 
to  see  on  one  and  the  same  tree,  branches  with  foUage  of 
different  colors  and  forms,  some  growing  slowly  and  some 
already  covered  with  side  branches  and  bearing  red,  yellow 
or  blue,  flat  and  round,  small  and  large,  ripe  and  unripe, 
sometimes  only  half-developed  fruits.  The  total  result  is 
strikingly  bizarre.  When  the  fruit  is  ripe,  Burbank  walks 
along  the  rows  of  trees,  marking  those  which  are  either 
decidedly  best  or  useless  as  far  as  can  be  judged  by  first 
examination.  Then  his  foreman  removes  all  those  which 
have  been  marked  as  valueless,  leaving  only  about  half  of 
the  stock  and  making  space  for  new  seedlings  to  be  grafted 


Fig.  68.     A.  The  plum.     B.  The  brown-leaved  Prunus  Pissardi,  two  species 
grafted  on  the  same  tree. 


215 


2i6  PLANT-BREEDING 

on  the  old  branches.  Afterward,  the  remaining  fruiting 
branches  receive  careful  investigation.  Their  number 
reaches  many  hundreds  each  year,  the  total  sum  of  all  his 
hybrids  amounting  to  some  three  hundred  thousand,  and 
having  afforded  the  selection  material  for  nearly  twenty 
seasons.  The  comparison,  of  course,  is  based,  in  the  first 
place,  on  the  inspection  of  those  hybrids  that  are  ripening 
their  fruit  at  the  same  time.  But  the  best  types  of  previous 
years  must  be  used  as  standards  in  the  work,  most  of  them 
bearing  fruit  for  a  second  or  third  time,  and  thus  facilitating 
the  comparison.  Finally  some  four  or  five  are  selected  as 
being  ready  for  the  trade,  and  these  are  then  multiphed  as 
rapidly  as  possible  and  offered  for  sale. 

The  remainder,  after  the  extirpation  of  all  minor  forms, 
^  yields  a  harvest  of  hybrid  seeds  for  the  next  sowing,  and  are 
themselves  destined  for  renewed  crosses  in  the  following 
year. 

In  his  selections,  Burbank  is  guided  by  a  special  gift  of 
judgment.  By  virtue  of  his  long  study  of  plums  and  by 
the  comparison  of  so  many  thousands  of  varieties  of  them, 
he  has  acquired  a  rare  and  comprehensive  knowledge  of 
all  their  qualities,  which  enables  him  to  tell  on  his  farm, 
which  kinds  are  the  best  for  shipping,  which  for  canning 
purposes,  which  will  be  household  fruits,  and  which  good  for 
drying.  He  knows  his  trees,  observes  their  behavior  during 
the  winter,  pays  attention  to  the  vigor  of  their  growth  and 
the  mode  of  their  development,  and  from  the  inspection  of 
all  these  quahties,  can  distinguish  the  hardy  varieties  from 
the  unresistant  ones,  and  predict  for  each  the  region  and  the 
life  conditions  under  whicn  it  will  probably  thrive.  To  a 
large  degree  Ms  choice  is  guided  by  such  considerations, 
and  anyone  who  has  a  lesser  experience  in  the  selection  of 
prunes  can  hardly  understand  how  it  is  at  all  possible  to 
choose  the  right  kinds  for  their  distinct  uses,  but  the  success 


BURBANK'S   HORTICULTURAL   NOVELTIES     217 

which  his  creations  are  said  to  have  had  in  the  United  States, 
and  even  in  many  countries  of  the  old  world,  is  the  best 
proof  of  the  reliabiUty  of  liis  judgment. 

This  judgment  is  due  partly  to  his  genius  and  partly  to 
his  broad  experience  in  all  questions  of  practical  plant  breed- 
ing. But  its  appHcation  to  a  definite  group  of  hybrids  rests 
chiefly  on  the  study  of  that  group  itself.  His  experience 
with  plums  will  enable  him  to  make  faster  progress  in  the 
study  of  hybrids  of  any  other  genus,  but  it  is  of  no  direct 
avail  for  the  practical  work  with  them.  ]\Iore  than  once  in 
our  discussions,  Burbank  has  laid  stress  on  tliis  point,  assert- 
ing that  each  new  family  has  to  be  stucUed  anew,  and  given 
the  same  care  and  devotion,  in  order  to  learn  all  about  its 
qualities  and  possibihties.  There  are,  of  course,  some  general 
rules,  but  the  ultimate  result  is  mainly  dependent  upon  a 
thorough  knowledge  of  all  the  characters  which  may  have  or 
may  afterwaid  gain  some  influence  in  directing  selection. 

All  these  considerations  are,  however,  related  to  the  work 
of  crossing  and  selecting,  which,  as  we  have  seen,  is  only 
the  second  part  of  the  whole  study.  The  first  part,  insuring 
half  of  the  result,  is  the  primary  choice  of  the  varieties  to 
start  from.  These  have  to  include  as  many  profitable 
qualities  as  are  at  the  time  available,  but  this  part  of  the 
work  is  manifestly  to  be  continued  along  with  the  crossing. 
He  must  be  constantly  on  the  lookout  for  new  types,  and 
whenever  attention  is  directed  to  newly- discovered  species, 
or  when  the  study  of  the  strains  points  to  desirable  qualities 
which  may  be  secured  by  the  use  of  older  native  forms 
which  have  not  been  tried  until  that  time,  new  introductions 
must  be  made.  By  increasing  the  number  of  the  parent 
species,  and  thereby  that  of  the  available  characters,  the 
range  of  variability  is  considerably  widened,  and  numerous 
possibilities  of  new  combinations  are  opened.  From  this 
point  of  view,  I  now  mention  the  introduction  of  the  cherries 


2i8  PLANT-BREEDING 

and  the  apricots  into  the  hy1)rid  pkuii  famihes.  The  cross 
between  the  cherry  and  the  pknn  was  readily  made,  and  the 
hybrids  were  abundantly  fertile.  A  new  element  was  in- 
troduced by  two  evergreen  cherries,  one  of  the  Pacific  coast 
and  one  from  Mexico.  Thes(>  were  easily  crossed,  both 
with  deciduous  cherries  and  with  plums,  but  the  results  are 
still  awaiting  selection  and  improvement. 

The  hybrids  of  the  plums  and  apricots  are  called  by 
Burbank  i)lumcots,  and  a  certain  number  of  these  most 
deHcious  and  beautiful  fruits  1  have  seen  on  his  farm  at 
Sebastopol.  They  have  the  outer  appearance  of  apricots 
but  combine  the  rich  and  varied  colors  of  the  prunes  with 
the  soft  indument  of  the  former.  Dark  blue  and  downy 
apricots  are  as  striking  a  novelty  to  the  eye  as  the  combina- 
tion of  the  flavor  of  prunes  and  apricots  in  one  fruit  is  flat- 
tering U)  the  taste.  Some  had  a  yellow  fruit  flesh,  in  others 
it  was  red  or  pink  or  nearly  white.  The  dark  red  varieties 
seemed  to  me  the  most  juicy,  and  were,  perhaps,  to  be  the 
next  to  be  definitely  selected.  Some  plumcots  have  free 
stones,  but  others  were  chng  stones.  In  many  other  respects, 
striking  chflerences  were  observed,  giving  an  almost  com- 
plete material  for  liis  selections. 

It  is  difficult  to  tell  whether  the  range  of  possibilities  of 
the  crossings  of  plums  has  reached  its  ultimate  limits  or 
whether  it  will  afterward  assume  still  more  astonishing 
aspects.  The  cross  between  apricots  and  the  Japanese 
plum  has  been  attended  with  difflculty,  and  has  succeeded 
only  by  the  use  of  distinct  varieties.  Peaches  should  next 
come  up  for  trial,  but  their  crosses  with  plums  have  been 
devoid  of  success  until  now.  But  perhaps  some  of  the  hy- 
brid strains  may  be  more  suitable  than  others,  and  new 
attempts  may  succeed  where  older  ones  have  miscarried. 
In  case  of  success  in  this  new  hne,  the  range  of  possibiUties 
will  become  almost  inexhaustible. 


BURBANK'S   HORTICULTURAL   NOVELTIES     219 

Lea\ing  our  sketch  of  the  historical  evidence  given  by 
Burbank  concerning  liis  hybrids,  some  points  of  biological 
interest  remain  to  be  mentioned.  In  the  iirst  place,  crosses 
are  by  no  means  always  successful.  The  result  depends 
mainly  upon  the  affinity  of  the  chosen  parents.  Whenever 
their  systematic  differences  are  too  great,  the  cross  will  be 
infertile,  or  at  least  the  produced  hybrids  will  refuse  fertil- 
ization, even  with  the  pollen  of  their  parents.  Repeated 
crosses  are  impossible  and  no  practical  results  can  be  ob- 
tained. Or  all  the  hybrids  may  be  of  inferior  ciuaHty,  not 
promising  any  impro\-ement  and  thus  are  not  worthy  of 
further  culture.  Of  this,  Burbank  gives  an  instance  in  an 
experiment  with  a  Californian  dewberry.  He  transplanted 
a  specimen  of  this  indigenous  species  into  his  garden,  isolated 
it,  and  brought  to  its  blossoms  the  pollen  of  almost  all  its 
alUes  he  had  at  that  time  under  cultivation.  He  gave  it 
the  pollen  of  brambles  and  raspberries,  of  strawberries  and 
roses  and  even  of  cherries,  apples,  and  pears.  All  the  seed 
was  saved  in  a  mixture  and  a  strange  lot  of  hybrids  arose 
from  them  the  next  spring.  Some  repeated  well  know^n 
types,  but  many  seemed  full  of  promise  of  new  forms.  At 
the  blooming  period,  many  defaulted,  making  no  IIowxts  at 
all,  and  the  remainder  proved  to  be  utterly  sterile;  no  single 
hybrid  could  be  chosen  by  which  a  new^  strain  could  be 
obtained. 

A  parallel  instance  is  that  of  the  Nicotunia.  This  is 
Burbank's  name  for  a  hybrid  he  once  won  between  a  tobacco 
plant  and  a  Petunia.  The  parents  are  so  distant  that,  as  a 
rule,  the  cross  never  results  in  good  seeds.  Among  hundreds 
of  seedless  capsules,  he  found  one  in  a  better  condition,  and 
from  its  contents  raised  one  single  plant.  This,  however, 
was  an  annual  and  absolutely  sterile  and  so  the  experiment 
ended  with  its  death. 

A  last  point  which  we  have  to  discuss  is  the  interest 


2  20  PLANT-BREEDING 

attached  b}'  the  practical  breeder  to  the  purity  of  his  fer- 
tilizations. Of  course,  in  scientific  investigations,  the  father 
is  of  equal  importance  with  the  mother,  and  the  utmost  care 
has  to  be  taken  that  the  stigma  is  covered  with  pure  pollen. 
Moreover,  in  the  pedigree,  the  lines  of  the  male  ancestors 
rerjuire  the  same  care  as  the  female  line.  Exact  and  elaborate 
book-keeping  is  the  rule,  and  no  single  pollination  should 
be  made  that  is  not  thoroughly  controlled  and  registered. 

In  practice,  however,  such  a  susceptibility  would  be  as 
impossible  as  useless.  The  proof  of  the  pedigree  is  not  the 
aim  of  the  experimenter.  He  only  looks  for  the  result.  In 
crossing  six  or  seven  species  and  hundreds  of  their  hybrids, 
the  pollen  is  brought  from  one  flower  to  the  other,  as  oppor- 
tunity is  offered.  Hundreds  of  crossings  may  be  made  in  a 
few  hours,  and  their  seed  may  be  saved  in  mixture  without 
special  care,  or  too  much  loss  of  time.  If,  however,  each  of 
these  crosses  has  to  be  kept  separate,  to  be  labeled  and 
registered,  and  its  seed  sown  apart  from  the  others,  the 
amount  of  work  will  increase  a  hundred-fold  without  any 
chance  of  giving  more  or  more  profitable  hybrids. 

Separate  pedigree  book-keeping  being  thus  impossible, 
small  impurities  of  the  pollen  cannot  be  avoided  and  are  not 
to  be  noticed.  Pollen  is  brought  by  the  finger  to  the  stigma, 
but  a  breeder  would  simply  laugh  at  the  idea  of  a  scientific 
investigator  washing  his  hands  between  successive  pollina- 
tions, or  inspecting  his  fingers  with  a  lens  in  order  to  remove 
some  stray  remaining  pollen  grains  Quite  on  the  contrary, 
such  unintentional  crosses  often  bring  greater  chances  of 
unexpected  success  than  the  regular  and  contemplated  pollin- 
ations, and  if,  perchance,  they  give  hybrids  of  inferior  quality, 
the  damage  is  only  small,  since  the  offspring  is  sure  to  be 
eliminated  by  the  next  selection.  Thus  we  see  that  some 
freedom  must  be  allowed  in  the  choice  and  in  the  purity  of 
the  pollen.     But,  on  the  other  hand,  it  is  easily  seen  that  much 


BURBANK'S   HORTICULTURAL   NOVELTIES     221 

caution  is  to  be  observed  in  the  scientific  interpretation  of  the 
breeder's  results. 

As  a  general  rule,  we  may  state  that  the  broad  Hnes  of 
practical  hybridizing  and  selection  afford  liighly  valuable 
resources  for  theoretical  discussions,  but  that  on  single 
points  they  should  not  be  accepted  as  definite  proofs,  but 
only  as  indications  for  more  sharply  circumscribed  experi- 
ments. Even  with  this  restriction,  however,  the  value  of 
Burbank's  work  for  the  doctrine  of  evolution,  compels  our 
highest  admiration. 

D.  IVrUTATIONS  IN  HORTICULTURE 
For  the  larger  number  of  horticultural  varieties  we  do 
not  know  the  origin.  Many  of  them  are  older  than  the  his- 
torical records,  others  have  been  found  in  the  wild  state  or 
in  foreign  countries  or  in  old-fashioned  gardens.  A  certain 
number  appeared  in  nurseries  and  cultures,  but  their  first 
generations  were  overlooked  and  they  were  appreciated  only 
when  it  was  already  too  late  to  study  their  first  appearance. 
Whenever  this  first  appearance  has  been  noted  and  re- 
corded the  development  of  the  variety  took  one  or  two  or  a 
small  number  of  years.  Sometimes  it  appeared  with  the 
full  display  of  its  qualities  and  proved  constant  from  seed 
from  the  very  beginning.  But  such  cases  are  rare.  Ordi- 
narily it  was  discovered,  at  first,  in  a  very  imperfect  and  often 
scarcely  perceptible  degree  of  development,  or  it  was  not 
constant  from  seed.  In  both  cases  it  had  to  be  developed 
by  selection  in  order  to  insure  a  normal  degree  of  purity  and 
constancy.  This  process  requires  some  years,  and  their 
number  is  different  for  different  species,  according  to  their 
capacity  for  self-fertilization,  their  fertihty,  and  other  factors. 
Whenever  the  varietal  mark  is  plain  in  the  first  year, 
selection  has  only  to  produce  constancy.  This  might  be 
attained  at  once,  if  the  visits  of  insects  could  be  excluded, 


222  PLANT-BREEDING 

either  l)y  isolation  or  by  covering  the  flowers  and  fertiUzing 
them  artificially.  If  this  is  done,  the  varieties  prove  con- 
stant, with  few  exceptions.  In  practice,  however,  isolation 
and  artificial  fecundation  are  often  too  cumbersome,  and  the 
easier  way  by  repeated  selection  is  preferred.  Gradually 
it  ehminates  the  effects  of  the  natural  crosses  with  the  neigh- 
boring varieties  and  in  three  to  five  years  it  ordinarily  brings 
the  purity  up  to  the  degree  required  for  commercial  purposes. 

If,  however,  the  varietal  mark  should  show  itself  only 
imperfectly  in  the  Iseginning,  being  limited  to  a  supernum- 
erary petal,  to  a  shght  indication  of  a  new  color,  to  a  fine 
line  of  a  different  hue,  or  to  a  hardly  perceptible  fragrance, 
selection  has  to  improve  it.  In  the  case  of  pure  and  artifi- 
cial polUnation  the  ordinary  variabihty  of  the  new  mark 
would  bring  it  to  its  main  condition  as  soon  as  the  sowings 
reach  the  required  extent,  but  in  practice  the  process  must 
be  combined  with  the  described  gradual  elimination  of  the 
effects  of  crosses,  by  which  it  is,  of  course,  made  much 
slower.  Four  to  five  years,  however,  are,  as  a  rule,  sufficient 
to  reach  the  aim. 

The  wav  in  which  all  these  varieties  originate  is  best  ex- 
pressed by  the  technical  term  of  chance  seedlings.  Fruit- 
groAA'crs,  nurserymen,  and  amateurs  are  always  on  the  look- 
out for  such.  Even  among  the  commercial  growers  there  is 
a  regular  search  for  deviations  in  the  direction  of  improve- 
ment. Any  seedling  that  chances  to  show  more  desirable 
characters  than  the  average  will  be  noted  and  cared  for.  To 
this  cUscriminating  search  is  due  the  superiority  of  some  of 
the  leading  varieties  of  fruit-trees,  which  have  been  recog- 
nized as  meeting  special  requirements  and  have  been  multi- 
pHed  accordingly.  Such  chance  seedHngs  occur  every- 
where, from  time  to  time,  but  the  cause  of  their  appearance 
is,  as  yet,  whoUv  unknown.  The  only  thing  we  know  about 
them  is  that  among  large  numbers  the  chance  of  finding 


BURBANK'S   HORTICULTURAL   NOVELTIES     223 

them  is  greater  than  in  small  cultures.  In  small  private 
gardens  they  are  very  rare,  but  in  large  nurseries  they  will 
hardly  ever  fail,  although  they  may  often  be  much  rarer  than, 
for  example,  one  in  a  year. 

Hybridizing  being  one  of  the  most  important  proce- 
dures in  many  of  the  larger  nurseries,  the  cjuestion  has  often 
been  raised  whether  such  chance  seedlings  should  be  more 
frequent,  or  rarer,  after  crossing  than  in  pure  strains.  Of 
course,  tliis  question  is  of  the  highest  practical  as  well  as 
scientific  interest,  because  if  it  had  to  be  answered  in  the 
affirmative,  at  least  one  possible  cause  would  be  indicated. 
It  seems  quite  possible  that  such  should  be  the  case,  and 
even  our  knowledge  concerning  the  numerical  laws  of  the 
spHtting  of  a  hybrid  progeny  does  not  exclude  the  possibiUty 
that  among  a  thousand  and  more  offspring  some  chance 
deviation  may  occur.  As  yet,  however,  the  evidence  at 
hand  is  too  rare  to  justify  a  definite  conclusion. 

In  this  respect  the  same  conchtions  prevail  on  Burbank's 
farms  as  everywhere  else.  Of  course,  sports  occur  quite 
often  and,  in  many  cases,  may  even  be  produced  at  will.  But 
sports  include  a  wider  range  of  variabihty  than  the  chance 
seedlings.  The  latter  can  always  be  considered  as  sports, 
but  not  all  sports  belong  to  this  same  group.  A  critical 
review  of  some  of  the  most  interesting  sports  among  the  cul- 
tures of  Santa  Rosa  and  Sebastopol  will  best  prove  this,  and 
at  the  same  time  it  will  give  an  opportunity  to  convey  a  still 
clearer  idea  of  the  bearing  of  Burbank's  methods  and  results 
on  the  science  of  evolution. 

In  the  first  place,  the  occurrence  of  elementary  species 
in  nature  often  opens  definite  joossibihtics  for  culture  and 
selection.  Burbank  showed  me  a  highly  interesting  sport 
of  a  Mahalcb  cherry  or  Prunus  Mahalcb.  It  grew  in  a  Uttle 
grove  of  shrubs  of  the  same  species,  on  his  Sebastopol  farm. 
It  had  vellow  berries  instead  of  black  ones  and  showed  some 


224  PLANT-BREEDING 

corresponding  smaller  deviations  from  the  average  type. 
He  uses  the  species  for  stocks  for  grafting  and  had  sown  them 
from  seed  which  he  had  received  from  the  southern  states. 
From  one  of  these  introduced  seeds  the  sport  had  arisen. 
There  could  be  no  doubt  that  it  was  due  to  a  real  mutation, 
and  it  was  manifest,  also,  that  tliis  had  been  produced  be- 
fore the  introduction.  But  whether  the  deviating  specimen 
itself  was  to  be  considered  as  a  mutant,  or  whether,  perhaps, 
in  the  original  locality  an  old  yellow  variety  of  Mahaleb 
cherry  existed,  he  could  not  tell.  It  was  noticed  here  for 
the  first  time,  but  whether  it  was  old  or  new,  nobody  knew. 
It  was,  however,  a  most  typical  sport.  Elementary  species 
among  trees  have  not  yet  been  given  the  interest  wliich  they 
deserve.  The  apples,  pears,  hawthorns,  and  some  others 
have  yielded  numerous  types,  either  for  industrial  culture  or 
for  scientific  description.  Oaks  and  walnuts  differ  in  the 
same  way,  and  there  can  hardly  be  any  doubt  that  this 
is  true  for  a  large  number  of  deciduous  and  even  of  conif- 
erous trees,  also.  A  scientific  distinction  and  industrial 
test  of  these  elementary  species  might  probably  lead  to  a  dis- 
tinct improvement  of  many  of  our  forests  and  groves,  giving 
more  uniform  crops  of  nuts,  or  harder  and  better  lumber,  or 
a  more  rapid  growth,  or  more  straight  and  less  branched 
stems,  etc.  A  combination  of  the  results  wliich  Nilsson  ob- 
tained by  his  sharp  distinction  of  the  elementary  species  of 
cereals,  \rith  the  possibilities  indicated  by  the  hybrid  walnuts 
and  other  trees  of  Burbank,  might  open  large  prospects  of 
improvement  in  forestry. 

In  many  cases  it  is  doubtful  whether  a  sport  is  due  to  a 
mutation  or  to  extreme  fluctuating  variability.  The  fra- 
grant varieties  of  Calla,  Dahlia,  and  Verbena  may  be  cited 
as  instances.  The  first  of  them  has  already  been  alluded  to, 
but  the  production  of  the  two  others  deserves  a  more  detailed 
description.     Along  the  fence  of  liis  garden,  in  front  of  his 


BURBANK'S   HORTICULTURAL   NOVELTIES     225 

house,  a  large  row  of  fragrant  Verbenas  was  in  full  bloom, 
at  the  time  of  my  last  visit.  It  was  the  ordinary  European 
garden-type,  but  of  a  uniform  pale  pink  color.  All  of  them 
were  manifestly  derived  from  cuttings  from  one  individual. 
They  had  the  most  deUcious  flavor  of  the  traihng  Arbutus, 
Epigeia  repcns,  a  much-beloved  creeping  herb  of  the  eastern 
woods.  Burbank  told  me  that,  years  ago,  when  busy  in  the 
selection  of  his  Verbenas,  he  was  struck  by  a  faint  odor  from 
some  of  the  flowers.  He  did  not,  however,  succeed  in  sin- 
gling out  the  fragrant  individual.  Next  year,  he  noticed  the 
same  odor  and  was  able  to  isolate  the  sporting  plants.  He 
saved  and  sowed  their  seeds,  got  better  scented  specimens 
among  the  offspring  and  selected  and  isolated  these.  After 
some  years  of  selection  the  fragrance  was  noticeably  in- 
creased and  the  variety  received  the  name  of  "Mayflower." 
It  is  not  constant  from  seed  and  it  is  not  known  whether  it 
can  be  made  so  or  not.  Ordinary  Dahlias  have  a  some- 
what disagreeable  odor.  Tliis  has  been  driven  out  and 
replaced  by  the  sweet  fragrance  of  a  magnolia  blossom  of 
the  glauca  species.  The  origin  of  this  race  was  a  single 
plant  with  a  faint  fragrance,  which  Burbank  noticed,  several 
years  ago,  on  one  of  his  beds.  Through  isolation  and  repeat- 
ed selection  the  fragrance  has  been  increased  and  fixed,  and 
the  variety  purified  from  its  hybrid  admixtures,  but,  as  yet, 
it  is  not  sufticiently  fixed  to  reproduce  itself  purely  from  seed. 
Whether  the  original  variant  was  itself  a  hybrid  between  an 
unnoticed  fragrant  parent  and  the  ordinary  form,  or  only  a 
minus- variant  of  the  new  fragrant  variety,  it  is  now,  of  course, 
impossible  to  decide. 

Fragrance  in  fruits  is  often  discovered  and  improved,  in 
the  same  way,  by  Burbank.  Even  among  walnuts  he  has 
produced  a  fragrant  variety.  More  interesting,  from  a  prac- 
tical as  well  as  from  a  scientific  point  of  view,  is  the  sweet 
v/alnut  which  lacks  the  bitter  tannin  in  the  coat  of  its  nuts 


226  PLANT-BREEDING 

and  in  the  thin  shell  of  its  seed.  As  a  variety  it  has  been 
given  the  name  of  wliite  walnut.  Its  nuts  are  white  and  do 
not  need  the  artificial  bleaching  of  the  other  sorts  to  which 
the  tannin  of  the  coats  gives  their  dark  appearance.  The 
pit  on  the  inside  of  the  nut  is  of  a  pure  white  and  sweet, 
because  the  astringent  taste  of  the  shell  and  the  meat  has  been 
taken  away  from  it.  This  variety  was  started  from  some 
of  his  hybrid  nuts  which,  at  first,  gave  some  indication  and 
promise  of  success  in  this  Une  of  improvement. 

In  contrast  to  these  pure  sports  I  now  mention  the  cases 
in  which  a  combination,  obtained  by  means  of  a  cross,  is 
so  strikingly  different  from  what  could  be  expected  that  it  is 
instantly  designated  a  "sport."  The  Bartlett  plum  is  such 
a  chance  seedHng  among  the  plum  hybrids  of  the  Sebastopol 
farm.  We  inspected  the  tree,  but  the  fruit  was  not  yet 
ripe.  It  is  (juite  different  from  other  plums.  It  branched 
from  its  \'ery  base  and  had  erect  shoots  with  a  fine  peculiar 
foUage.  Its  plums  have  the  taste  and  fragrance  of  a  Bartlett 
pear,  and  even  the  meat  resembles  that  of  this  well-known 
fruit.  Msitors  whom  Burbank  reciuested  to  eat  it  with 
their  eyes  shut,  have  taken  it  for  a  pear.  It  sprang  up  in  a 
lot  of  hybrid  seedhngs,  most  of  which  had  been  produced 
by  crossing  the  Kelsey  and  the  Simoni,  but  for  this  individ- 
ual seedling  the  ancestry  could  not  he  traced.  It  is,  how- 
ever, an  evident  combination,  and  all  of  its  cjuahties  can  be 
traced  to  its  probable  parents,  the  flavor  being  mainly  due 
to  the  Prunus  Simoni. 

The  stoneless  prunes  and  the  spineless  edible  cacti 
are  such  evident  hybrids  that  it  is  doubtful  whether  anybody 
would  designate  them  as  sports.  I  have  already  given  a 
general  description  of  them,  but  shall  now  add  some  details. 
About  the  year  1887,  Burbank  received  his  first  "prune  sans 
noyau"  from  a  French  nurseryman.  It  soon  fruited  and 
produced  a  fruit  about  the  size  of  a  small  cherry.     It  was 


227 


228  PLANT-BREEDING 

crossed  with  the  French  prune,  Petite  d'Agen,  wliich  is 
widely  spread  in  Cahfornia  culture,  and  with  other  prunes. 
About  1893,  the  first  hybrid  fruits  ripened.  Numerous 
crosses  had  been  made,  numerous  hybrids  had  to  be  tested. 
Only  a  small  proportion  of  the  scedUngs  were  stoneless,  and 
most  of  these  showed  the  undesirable  quahties  usually  found 
in  seedhngs.  It  was  only  in  1899  that  a  good  palatable 
stoneless  prune  of  sufficient  size  appeared.  This  has  been 
given  the  name  of  Miracle,  and  is  now  being  brought  into 
the  trade  by  the  Oregon  Nursery  Company,  at  Salem, 
Oregon.  It  combines  the  main  character  of  the  "prune sans 
noyau"  with  the  good  quahties  of  the  Petite  d'Agen,  while 
hardiness  and  bearing  qualities  arc  characteristics  of  both 
parents.  It  does  not  contain  sugar  enough  to  be  classed 
among  the  drying  prunes,  but  for  cooking  it  must  supplant 
the  well-known  Damsons,  being  larger  and  more  productive 
than  any  of  them. 

The  spineless  edible  cactus  combines,  in  the  same  way, 
the  main  character  of  its  spineless  parent  with  the  excellent 
cjuahties  of  the  ordinary  cultivated  varieties.  It  has  excel- 
lent fruit  of  a  new  flavor  which  may  be  eaten  fresh  or 
cooked.  As  food  for  cattle  the  stems  are  very  rich;  they  are 
estimated  to  be  at  least  one  half  as  nutritious  as  alfalfa  (Lu- 
cerne clover).  The  production  of  this  variety  started  from 
five  species  of  Opuntia  imported  from  different  countries, 
the  names  of  some  of  them  being  unknown  at  the  time. 
Among  them  was  a  spineless,  but  small  and  insignificant, 
species  from  Central  America.  These  he  has  crossed  and 
re-crossed  with  the  cultivated  varieties,  selecting  for  vigorous 
growth  and  superior  food-bearing  (jualitics.  A  number  of 
European  and  African  varieties  of  Indian  Figs  were  sent  to 
him  and  the  Opuntia  vulgaris,  O.  Engelmanni,  and  other 
hardy  types  were  mixed  with  them.  The  beds,  which  I  saw 
in   1906,  showed  hundreds  of  specimens  which  had  been 


3 
c5' 


n 


229 


230  PLANT-BREEDING 

planted  in  the  spring  and  had  already  produced  a  first  set 
of  numerous  disc-like  branches.  They  were  expected  to 
make  two  or  three  more  sets  in  the  same  year  and  to  fill  in 
the  large  spaces  which  were  left  between  them  at  the  time 
of  their  planting.  They  varied  in  the  size,  form,  and  color 
of  the  pods,  and  probably,  also,  in  their  nutritious  qualities, 
and  were  grown  as  a  direct  test  of  these  points.  The  value 
of  these  hundreds  of  plants  which  will,  on  the  average, 
produce  fifty  pods  each  in  a  year,  may  l)e  deduced  from  the 
fact  that  he  had  sold  Uvc  of  the  pods  to  an  Australian  firm 
and  was  Ijuilding  a  iiew  and  larger  residence  from  the  sum 
they  had  brought  him. 

It  would,  of  course,  add  highly  to  the  value  of  this  race 
if  it  could  be  made  constant  from  seed.  It  is  evident  that 
a  rapid  spreading,  as  well  as  the  treatment  on  the  farms, 
would  be  made  more  easy  by  such  a  change.  I  saw  numer- 
ous wooden  seed  boxes  with  small  scedhngs,  but  almost  all 
of  them  were  spiny.  Thousands  were  rejected,  and  only  those 
which  showed  a  cUstinct  diminution  of  their  spines  were 
selected  and  planted  out.  Large  beds  with  young  spineless 
plants  were  seen  in  his  garden.  Burbank  estimates,  from 
the  present  extension  of  uncultivated  lands  fit  for  the  pro- 
duction of  cacti,  that  his  spineless  and  edible  varieties  may, 
in  time,  double  the  population  of  the  earth.  At  least  they 
promise  to  do  more  for  the  world,  in  a  material  way,  than 
any  other  of  his  productions,  but  much  work  will  still  be 
required  before  even  an  essential  part  of  his  hopes  can  be 
brought  into  execution. 
,  Beautiful  and  striking  sports  are  sometimes  offered  by 
hybrids  which  revert  to  a  quality  of  one  or  more  of  their 
pure  ancestors,  this  mark  not  yet  being  displayed  in  the 
previous  hybrid  generations.  An  instance  of  this  we  admired 
among  his  Callas.  Hitherto  his  hybrids  had  varied  in  the 
color  of  their  spathes  from  white  to  a  more  or  less  intense 


3    O 


231 


232  PLANT-BREEDING 

yellow.  During  my  last  visit  one  of  the  seedlings,  however, 
opened  its  sheath  with  a  purple  color,  reminding  us  of  its 
forefathers,  Rehmannii  and  Nelsonii,  with  their  pink,  rose, 
and  purphsh  hues.  But  in  this  hybrid  the  color  was  deep- 
ened, covering  almost  the  whole  of  the  flower,  and  was  thus 
evidently  improved. 

Hybrid  poppies  are  Hable  to  reversions,  also.  Burbank 
crossed  the  oriental  poppy,  which  is  a  perennial  herb,  with 
the  snow-white,  double  and  fringed  flowers  of  "the  Bride" 
and  some  other  varieties  of  the  common  opium  poppy.  I 
have  already  referred  to  these  crosses  and  their  high  degree 
of  variability.  On  my  last  \Tlsit,  I  saw  a  large  bed  in  full 
bloom  repeating  almost  all  the  known  color  varieties  of 
double  poppies,  and  varying  in  many  other  cUrections.  He 
also  crossed  this  Bride  variety  and  some  others  with  a  wild 
and  scarcely  cultivated  smaller  species,  the  Papaver  pilosum, 
which  has  pale  orange  flowers.  Among  the  offspring  some 
were  fringed  and  some  double,  but  the  most  curious  fact  was 
that  some  produced  colors  not  intermediate  between,  or  like, 
those  of  the  varieties  named,  but  returning  to  the  original 
type  of  the  whole  somniferum  species.  The  special  causes 
of  these  atavistic  reversions,  however,  remained  obscure. 

Bud  sports  are  one  of  the  most  typical  kinds  of  sports. 
Burbank  cultivated  one  of  them.  Tt  was  the  Pierce's  grape, 
wdiich  originated,  some  time  ago,  as  a  branch  on  an  Isabella 
grape  on  ]\Ir.  Pierce's  farm  at  Santa  Clara,  Cal.  It  is  well 
known  for  its  large  and  superior  fruit.  It  comes  true  from 
seed  but  is  hable  to  sport  in  this  way  from  time  to  time.  The 
sporting  seedHngs  differed  from  the  average  in  the  shape, 
color,  and  hairiness  of  their  foliage  and  in  their  mode  of 
growth;  but,  at  the  time  when  I  inspected  them,  they  were 
still  too  young  to  produce  fruit. 

Other  bud  sports  Burbank  has  not  observed,  so  he  told 
me.     Of  course,  the  sports  with  variegated  leaves  are  to  be 


BURBANK'S   HORTICULTURAL   N0\T:LTIES     2: 


excluded.  Such  arc  common  in  almost  all  the  larger  nur- 
series. Sometimes  they  come  from  buds,  sometimes  from 
seeds.  A  case  of  the  latter  belonged  to  a  hybrid  between 
the  oriental  and  the  opium-poppy,  of  wliich  he  showed  us 
three  large  specimens  with  the  fohage  of  the  oriental  parent, 
but  with  beautiful  pale  yellow  borders  and  streaks  on  the 


Fig.  72.     A.  The  variety  of  the  Bride  of  the  Opium  Poppy.     B.  The  ^-ild 
species  Papaver  pilosum.     C.  The  hybrid  of  these  two  poppies. 

leaves.     It  scarcely  flowers  and  is  wholly  sterile,  but  may 
easily  be  multiplied  by  division. 

Whether  the  thornless  brambles,  previously  alluded  to, 
constitute  a  mutation  remains  to  be  investigated.  During 
the  days  of  my  last  visit,  they  flowered  for  the  first  time; 
their  long  stems  and  numerous  leaves  being  as  smooth  as 
when  the  plants  were  selected  from  the  seed  boxes. 


234  PT.ANT-BREEDING 

\  A  chestnut  without  spines  on  its  burs  was  growing  on 
the  Sebastopol  farm.  It  was  a  single  young  tree,  found 
among  the  numerous  offspring  of  a  cross  between  the  Japan- 
ese and  the  American  species,  both  of  which  have  spiny  burs. 
It  was,  probably,  a  pure  mutant. 

A  blue  p(^ppy  which  appeared  in  his  crosses  of  Papavcr 
Rhccas  and  allied  species  has  already  been  referred  to.  It 
was,  also,  ])robably,  a  pure  mutation,  which,  however, 
showed  itself,  in  the  beginning,  only  in  an  imperfect  degree 
of  development. 

\  The  same  holds  good  for  his  scarlet  California  poppy 
(Eschscholtzia  caHfornica).  He  discovered  the  first  indication 
of  this  mutation,  some  years  ago,  when  inspecting  large  beds 
of  ordinary  yellow  California  ]K)j)pies.  One  flower  caught 
his  eye;  it  had  on  one  of  its  petals  a  fine  longitudinal  line  of 
scarlet  color.  It  would,  surely,  have  escaped  the  eye  of 
most  other  men,  but  to  Burbank  it  betrayed  the  capacity  of 
this  one  plant  to  produce  a  variety  of  a  new  and  unsuspected 
color.  He  isolated  the  plant  and  saved  the  seed.  Among 
the  offspring  the  scarlet  color  was  repeated,  but  still  to  an 
insignificant  extent.  He  repeated  the  selection  during  some 
years  until  he  got  a  race  of  a  pure  and  uniform  scarlet  color 
in  all  the  flowers  and  on  all  the  plants.  We  saw  large  beds 
in  full  ])loom  l)ut  without  atavistic  reminders  of  the  yellow 
prototype. 

It  would  be  a  most  interesting  task,  full  of  promise,  to 
try  to  repeat  the  observation  of  the  appearance  of  all  these 
mutants  and  to  follow  their  origination  and  their  develop- 
ment under  the  rigid  conditions  of  scientific  research.  It 
might  be  expected  that  the  material  from  which  Burbank 
started  would,  probid^ly,  repeat  the  mutation,  even  as  other 
horticultural  and  experimental  mutations  are  known  to  have 
been  produced  repeatedly.  In  doing  so  an  exact  history 
might  be  given  instead  of  the  more  or  less  vague  and  incom- 


BURBANK'S    HORTICULTURAL   NOVELTIES     235 

plcte  reminiscences  of  the  breeder,  and  a  basis  might  be 
worked  out,  from  which  scientific  conclusions  of  the  highest 
importance  could  be  drawn.  Burbank  often  claims  that 
the  production  of  a  single  novelty  recjuires  much  time  and 
much  labor  and  a  considerable  amount  of  space  in  his  garden 
during  a  series  of  years.  The  scientific  repetition  and  de- 
scription of  such  a  mutation  experiment  would,  however, 
require  perhaps  ten  times  as  much  time  and  labor  as  the 
practical  production  of  the  same  variety. 

In  one  instance  I  have  had  the  good  fortune  of  producing 
experimentally  a  variety,  the  exact  counterpart  of  which  has 
been  produced  industrially  by  Burbank.  I  refer  to  the 
origin  of  a  double  marigold.  Burbank  is  doubling  his  Shasta 
daisy,  and  in  my  garden  I  observed  and  guided  the  springing 
up  of  a  double  form  of  the  }-ellow  corn-marigold  {Chrysan- 
themum segctum).  Although  Burbank's  description  of  this 
selection  is  only  very  short  and  succinct,  there  cannot  be  the 
least  doubt  concerning  the  parallehsm  of  the  two  cases. 
The  Shasta  daisy  is,  as  I  have  already  pointed  out,  a  hybrid 
between  a  Japanese,  an  American,  and  an  English  species  of 
the  genus  Chrysanthemum.  Among  them,  at  least  the 
English  ancestor  is  highly  variable,  and  it  is  evident  that  the 
fluted  rays,  and  some  other  remarkable  deviations  which 
occurred  in  the  hybrids,  may  be  due  to  this  source.  The 
same  holds  good  for  the  doubling.  Ten  or  fifteen  years  ago 
Burbank  discovered  a  slight  degree  of  augmentation  in  the 
number  of  the  ray-florets  of  some  of  his  hybrids.  He  care- 
fully isolated  them,  observed  an  increase  in  the  deviation 
and  repeated  the  selection  until  the  flower  heads  became  as 
double  as  those  of  any  other  double  variety  among  the  Com- 
posites. 

In  the  case  of  my  yellow  corn-marigold  the  selection  has 
been  accompanied  by  the  counting  of  the  ray-florets  for  all 
the  plants  of  the  succeeding  generations.     The  first  indica- 


236  PLANT-BREEDING 

tion  was  one  supernumerary  ray  on  each  of  two  flower  heads 
of  a  single  plant.  Sowing  the  seeds  of  this  individual,  the 
numbers  were  seen  to  increase  rapidly  but  all  the  ray-florets 
always  belonged  to  the  outer  rows  of  the  heads.  After  a 
selection  of  three  years,  suddenly  an  individual  appeared 
which  had  some  stray  ray  florets  scattered  among  the  tubular 
florets  of  the  center  of  some  of  its  latest  flowers.  The  seeds 
of  this  plant  at  once  gave  the  desired  double  variety.  All 
the  progeny  produced  more  or  less  double  flower  heads,  the 
number  of  the  rays  ranging,  in  the  l^est  instances,  from 
100  to  200.  In  the  following  year,  the  race  could  be  some- 
what purified  and  thereby  improved,  but  the  type  was  not 
essentially  changed  and  has  since  remained  constant.  The 
appearance  of  the  first  ray-florets  among  the  little 
central  tubes  would,  of  course,  easily  have  been  overlooked 
and  the  increase  of  the  number  of  the  rays  would  have  seemed 
gradual  throughout.  The  selection  would  have  obscured 
the  mutation,  as  has,  probably,  l)een  the  case  in  the  produc- 
tion of  many  other  horticultural  varieties. 


V 

THE    ASSOCIATION    OF    CHARACTERS    IN 
PLANT-BREEDING 

A.      ASSOCIATION      OF    CHARACTERS    IN   NATURE 

The  doctrine  of  evolution  is  so  closely  associated  with 
the  interests  of  man  that  each  phase  of  its  broad  lines  of 
teaching  commands  our  special  attention.  Amelioration 
of  domestic  animals  and  plants  is  one  of  the  prevaihng  feat- 
ures in  ao-riculture  and  horticulture.  The  laws  wliich 
govern  these  practical  endeavors  as  well  as  the  scientific 
investigations  are  now  being  slowly  disclosed.  Many  of 
the  common  cjuestions  which  puzzle  the  horticulturists  can 
be  answered  only  by  appealing  to  these  laws.  The  problems 
involved  are,  however,  many-sided  and  in  order  to  gain  a 
distinct  knowledge  and  a  clear  insight  into  their  different 
methods  of  research  it  is  nowadays  unavoidable  to  divide 
the  subject  into  its  separate  parts. 

Some  Hnes  of  research  may  guide  us  along  the  paths  of 
anatomical  and  histological  development;  others  are  related 
to  the  more  common  but  ccjually  significant  facts,  which  may 
be  gathered  by  observations  in  the  field.  These  latter  are 
vitally  related  to  the  study  of  organic  evolution,  and  often 
have  a  direct  bearing  on  the  practical  processes  of  breeding. 
Agricultural  plant-breeding  is  the  evolving  of  useful  qual- 
ities. But  what  are  qualities  and  how  may  they  be  discerned 
and  studied? 

For  many  years  this  (juestion  has  been  considered  as  a 
very  simple  one,  easily  to  be  answered  on  the  basis  of  our 
common  knowledge.  Of  late,  however,  this  attitude  has 
completely  changed,  and  the  intimate  nature  of  qualities 
and  characters  has  become  an  object  of  most  intense  inter- 
est for  the  practical  breeder  as  well  as  for  the  student  of 

237 


238  PLANT-BREEDING 

evolution.  Experience  has  taught  that  c|uaUties  are  often 
associated  with  one  another  by  distinct  laws,  and  that  a 
knowledge  of  these  laws  may  give  us  a  power  over  them, 
greater  than  any  man  has  heretofore  aspired  to.  Even  a 
suspicion  of  the  meaning  of  these  laws,  or  an  intuitive  appre- 
ciation of  their  work,  may  lead  to  valuable  results,  if  it  is 
only  combined  with  a  thorough  knowledge  of  the  species  in 
question. 

Before  going  into  the  details  of  my  subject  I  wish  to  con- 
vince my  readers  of  the  truth  of  these  assertions  by  giving 
some  noticeable  illustrations.  The  first  is  an  old  one,  the 
second  is  afforded  by  Burbank's  work,  and  the  third  is  taken 
from  Xilsson's  experiments  in  agricultural  breeding.  It 
will  not  be  necessary  to  go  into  many  details,  since  even  with- 
out them  their  bearing  will  be  clear  enough. 

The  common  stock  (Matthiola  incana)  is  cultivated  in 
double-flowered  and  in  single  varieties.  The  singles  are 
pure,  but  the  seed  for  the  doubles  is  saved  on  single- flowered 
syjecimens  belonging  to  the  same  variety.  From  these  seeds 
about  one  half  give  doul^le  and  the  other  half  single  flowering 
plants.  The  doubles,  however,  obtain  a  higher  price  on 
the  market,  and  it  is  therefore  of  some  interest  to  separate 
and  isolate  them  as  early  as  possible.  In  France  this  is 
done  by  children,  who  pick  out  the  singles  and  spare  the 
doubles.  This  is  done  while  the  plants  are  very  young, 
having  produced  a  little  stem  with  some  small  leaves,  but  still 
without  branches  and  without  flower  buds.  It  is  impossible, 
therefore,  to  distinguish  them  by  these  buds,  but  there  are 
slight  dift'erences  in  the  color  and  the  hairs  of  the  leaves, 
which  separate  the  doubles  from  the  singles  for  the  expe- 
rienced eye.  These  differences,  however,  are  so  very  slight 
that  it  is  impossible  to  put  them  into  words  or  even  to  explain 
them  to  the  layman.  No  botanist,  as  far  as  I  know,  has 
as  yet  succeeded  in  recognizing  them,  and  nevertheless  the 


THE   ASSOCIATION   OF    CHARACTERS  239 

children  of  the  nurseries  are  seldom  mistaken  in  their  choice. 
Hence,  we  may  conclude  that  the  character  of  the  doubles 
penetrates  the  whole  plant  and  produces  small  changes  in 
all  the  organs,  even  at  the  very  earliest  periods  of  their 
development. 

For  my  second  illustration  I  choose  Burbank's  selection 
of  quinces.  A  thorough  study  of  this  genus  has  enabled 
him  to  see  relations  between  the  quahties  of  the  fruits  and 
the  characters  of  the  foliage.  Thereby  it  has  been  possible 
for  him  to  judge  of  the  value  of  new  acquisitions  or  to  com- 
pare the  different  specimens  of  a  hybrid  culture,  long  before 
the  time  of  blooming.  Thousands  of  young  seedlings  may 
be  estimated  in  this  way,  the  unpromising  ones  being 
thrown  away  before  they  have  to  be  planted  out,  and  by 
this  means,  of  course,  much  space  and  labor  is  saved.  The 
differences  between  the  seedlings  are,  some  of  them,  so  great 
that  they  may  be  appreciated  by  other  people  too,  but  others 
are  so  shght  that  they  escape  general  observation.  But  in 
the  first  case  their  relation  to  the  qualities  of  the  fruit  is  hid- 
den from  the  eye  of  the  ordinary  horticulturist,  and  it  is  only 
by  means  of  a  special  knowledge  of  the  plant,  and  an  intui- 
tive appreciation  of  its  virtues  that  Burbank  could  make 
these  remarkable  selections. 

My  tliird  example  is  taken  from  the  selection  of  cereals 
on  which  Nilsson,  the  director  of  the  experiment  station  of 
Svalof  in  Sweden,  is  working.  The  barley,  as  cultivated  in 
the  central  parts  of  Sweden  for  the  purposes  of  the  brewers, 
was  generally  suffering  from  the  weakness  of  the  straw, 
which  caused  it  to  lie  down  in  unfavorable  summers,  thereby 
often  involving  the  loss  of  large  parts  of  the  harvest.  After 
many  years  of  unsuccessful  efforts  to  improve  this  barley 
in  order  to  give  it  stronger  halms,  Nilsson  decided  to  solve 
the  question  in  rjuite  another  way.  He  gave  up  the  selec- 
tion of  the  ordinary  sort,  the  so-called  ChevaHer  barley,  and 


240  PLANT-BREEDING 

proposed  to  look  for  tnc  same  qualities  among  other  sorts 
with  resistant  halms.  A  minute  study  of  the  botanical  char- 
acters of  the  ears,  of  their  spikelets  and  scales  led  him  to  the 
discovery  of  a  relation  between  the  form  and  the  hairiness 
of  the  latter  and  the  practical  cjuaHties  of  the  grains.  On 
the  ground  of  this  relation  tens  of  thousands  of  individual 
barley  plants  were  scrupulously  investigated,  and  some  sixty 
were  chosen  out  of  this  number  for  a  comparative  trial  of 
their  progeny.  Among  these  the  continued  study  during 
subsequent  years  led  to  the  selection  of  the  one  which  best 
answered  the  proposed  (|uestion,  inasmuch  as  it  combined 
the  quahties  of  a  fine  brewers'  barley  with  strong  and  resist- 
ant halms.  From  this  one  plant  a  race  has  been  derived, 
which  received  the  name  of  Primus-barley  and  has  already 
supplanted  large  parts  of  the  cultures  of  the  original  Che-\'a- 
lier  kinds  all  through  the  middle  parts  of  Sweden. 

These  examples  may  suffice  to  convince  us  of  the  useful- 
ness of  a  thorough  study  of  the  association  of  qualities  and 
characters  of  cultivated  plants.  Evidently  such  a  study  is 
a  very  difficult  one,  but  it  opens  new  and  broad  lines  of  re- 
search. In  order  to  build  upon  a  scientific  basis,  it  is  nec- 
essary not  to  confine  ourselves  to  cultivated  plants,  but  to 
take  as  large  a  view  of  the  whole  vegetable  kingdom  as  possi- 
ble. Only  in  this  way  is  there  a  chance  of  discovering  the 
great  laws  of  nature  which  govern  this  most  intricate  group 
of  phenomena. 

Broadly  speaking,  the  characters  of  plants  may  be  con- 
sidered from  a  systematic  or  from  a  physiological  point  of 
view.  The  systematist  explains  the  afimity  by  means  of 
the  laws  of  inheritance,  assuming  thereby  a  common  cause 
for  every  character  which  remains  unchanged  throughout 
a  large  group  of  closely  related  species.  The  flower  heads 
of  all  the  composites  must  have  one  and  the  same  cause,  and 
so  it  is  with  their  inferior  ovary,  their  connate  stamens,  and 


THE   ASSOCIATION   OF    CHARACTERS 


241 


many  other  characters.  Tliis  cause,  though  liidden  from 
our  eye,  and  showing  itself  only  in  its  effects,  must  be  the 
real  character,  which  by  means  of  heredity  has  come  to 
be  present  in  all  members  of  this  large  family.  We  may 
assume  it  to  be  pure  and  simple,  even  if  it  is  never  allowed  to 
show  itself  as  such,  but  must  always  become  visible  in  com- 
bination with  the  other  characters  of  the  same  species,  and 
may  be  changed  by  them  to 
a  greater  or  lesser  degree. 

The  physiologisc  has  re- 
marked, however,  that  the 
laws  of  heredity  cannot  be 
the  only  cause  of  the  simi- 
larity among  plants.  In 
innumerable  cases  there  is 
a  Hkeness  which  cannot  be 
explained  by  a  common 
origin.  The  spurs  of  the 
orcliids  and  of  the  violets, 
of  the  toadflax  and  of  the 
columbine  arc  evidently  the 
same  organs,  playing  every- 
where the  same  part  of  pro- 
ducing honey  for  the  visiting  insects.  Notwithstanding  their 
differences  in  size  and  color,  and  even  in  the  manner  of 
secreting  their  product,  there  can  be  no  doubt  as  to  the 
identity  of  the  primary  cause  wliich  has  produced  them. 
On  the  other  hand  the  plants  wliich  bear  them  belong  to  such 
widely  divergent  famihes,  that  it  is  simply  impossible  to 
look  for  a  common  origin  in  order  to  explain  tliis  repeated 
occurrence  of  spurs. 

So  it  is  in  almost  every  case,  for  characters  of  the  high- 
est systematic  value  as  well  as  for  minor  marks.  Inferior 
ovaries  are  found  among  dicotyls  and  among  monocotyls, 


Flowers  of  columbine,  show- 
ing the  spurs. 


242  PLANT-BREEDING 

gamopetalous  flowers  occur  in  the  mallows  and  in  the  hya- 
cinths, symmetrical  corollas  and  decussate  leaves  are  spread 
over  the  families  of  the  natural  system  in  the  most  capricious 
manner,  and  even  the  forms  and  structures  of  the  leaves  do 
not  show  any  relation  to  systematic  afimity.  Assuming  the 
same  causes  for  the  same  phenomena,  the  physiologist  is 
led  to  the  conclusion,  that  the  visible  characters  must  be  the 
result  of  internal  properties  which  may  be  the  same  in  widely 
different  groups  of  plants.  These  internal  qualities  may 
pass  from  species  to  species  by  the  laws  of  inheritance  or  be 
produced  anew  in  distant  families  and  genera. 

The  chemist  tries  to  connect  the  visible  properties  of  his 
substances  with  the  assumed  ({uaHtics  of  molecules  and  atoms, 
and  to  explain,  by  this  theory,  their  conformities  and  their 
divergencies.  In  the  same  way,  the  physiologist  explains  the 
likenesses  and  the  differences  of  his  })lants,  by  the  assump- 
tion of  ecjually  invisible  units,  which  are  supposed  to  under- 
lie the  visible  ])henomena.  These  units  he  calls  unit-char- 
acters. For  him  they  are  the  resting  pole  in  the  ever-mov- 
ing tide  of  the  outward  forms.  On  this  principle  he  tries 
to  explain  the  common  features  of  plants,  independently  of 
the  question  whether  they  are  closely  related  or  belong  to 
distant  groups.  It  is  a  wide  field  for  observations  and  induc- 
tions, but  the  study  heightens  our  appreciation  of  the  real 
nature  of  all  living  beings.  It  is  a  kind  of  biological  analy- 
sis, leading  to  a  knowledge  of  the  intimate  elements  of  which 
the  plants  are  built  up. 

The  study  of  these  elements  or  unit-characters  has  led 
to  the  discovery  of  a  most  significant  phenomenon.  It  is  the 
regular  coincidence  of  marks,  which  hitherto  had  been  re- 
garded as  quite  independent  from  one  another.  This  asso- 
ciation has  been  shown  to  obey  natural  laws,  and  the  study 
of  these  laws  enables  us  to  predict  one  mark  from  the  obser- 
vation of  the  other.     The  relation  of  the  color  and  form  of 


Fig.  74.  The  (it-adly  nightshade,  or  Atropa  Belladonna.  A.  Brown 
flower,  and  B.  Black  fruit  of  the  species.  C.  A  twig  of  the  yellow  variety 
with  pale  flowers  and  yellow  fruits. 


243 


244  PLANT-BREEDING 

the  young  seedlings  of  the  stocks  to  the  shape  of  the  flowers 
is  only  an  instance  of  the  general  phenomenon  of  association 
and  so  it  is  with  the  marks  which  enable  Burbank  and  Nils- 
son  to  make  their  selections. 

These  coincidences  are  called  technically,  correlations, 
and  it  is  these  which  I  have  chosen  for  the  subject  of  this 
chapter. 

Some  of  them  are  of  a  simple  and  obvious  nature,  and 
their  internal  cause  may  easily  be  understood  as  soon  as  the 
association  has  been  pointed  out.  Such  instances  may  serve 
as  a  basis  for  further  discussions,  and  become  a  guide  into 
the  more  intricate  cases. 

It  is  a  common  experience  that  many  color-varieties  of 
plants  may  be  distinguished  by  their  seeds.  This  rule  holds 
good  for  garden  plants  as  well  as  for  large  crops.  A  dark 
color  of  the  seed  indicates  a  bright  flower,  a  pale  seed  is 
usually  associated  with  white  or  pale  corollas.  Stocks  have 
grayish,  brown,  or  bluish  seeds  according  to  the  color  of  their 
petals.  Among  the  lupins  the  red  and  blue  forms  may  often 
be  distinguished  by  their  dark  seeds,  but  the  white  variety 
has  wliite  seeds  (Lupinus  angustifohus).  White  vetches 
have,  as  a  rule,  yellow  or  greenish  seeds,  in  contrast  to  the 
dark  seeds  of  the  common  species.  The  true  opium  poppy 
has  white  flowers  and  pale  seeds,  and  many  other  garden 
varieties  of  this  plant  differ  in  their  flowers  and  seeds  in  a 
more  or  less  corresponding  degree. 

In  all  such  cases  there  can  be  no  doubt,  that  the  coinci- 
dence is  a  real  correlation,  and  that  the  cause,  which  darkens 
the  flowers  is  the  same  as  that  wliich  is  active  in  the  seeds. 

Berries  often  show  the  same  correlation  to  the  flowers. 
If  a  species  has  red  or  blue  corollas  combined  with  dark 
berries,  its  white  variety  will  often  show  pale  or  even  white 
fruits.  One  of  the  most  interesting  instances  of  this  rule  is 
the  pale  variety  of  the  belladonna,  a  very  poisonous  plant. 


Fig-  75-     The   long-leaved   Veronica   {Venmica 
longijolia). 

245 


246  PLANT-BREEDING 

which  grows  in  many  forests  of  Germany.  It  has  brownish 
flowers  and  large  and  shiny  black  fruit,  the  color  consist- 
ing of  two  factors,  a  yellow  and  a  red  one.  A  variety  of  this 
species  was  discovered  by  Schiitz  in  a  wood  in  the  neighbor- 
hood of  Calw  in  Wurtemberg  about  the  middle  of  the  last 
century  (1851;  cf.  Hoffman,  Sp.  et  \'ar.,  p.  87).  It  has  pale 
greenish  flowers  and  bright  yellow  berries.  It  comes  true 
to  its  character  from  seed,  and  is  often  cultivated  in  botani- 
cal gardens.  The  red  dye  or  anthocyanin,  which  darkens 
the  corollas  of  the  species  and  is  concentrated  in  the  fruit 
to  a  degree  that  makes  it  black,  is  absent  in  both  organs 
in  the  variety,  the  yellow  not  being  affected  by  the  change. 
Evidently  the  red  dye  is  the  same  color  in  both  organs, 
and  as  soon  as  it  became  latent  by  the  production  of  the  new 
form,  it  disappeared  simultaneously  from  the  flowers  and 
from  the  fruits. 

In  many  species  this  anthocyanin  is  not  hmited  to  the 
flowers  and  the  fruits,  but  may  be  displayed  in  the  foHage 
also.  The  stem  and  the  branches,  the  leaves  and  their 
stalks,  and  even  the  bracts  of  buds  and  the  coats  of  a  bulb 
may  be  imbued  with  the  color.  It  very  often  happens  in 
such  cases  that  the  white  or  pale  varieties  show  their  marks 
in  the  correlated  organs.  As  the  first  example,  I  choose  the 
thorn-apples.  They  are  known  in  a  white  and  in  a  blue 
variety,  the  flowers  of  the  latter  being  of  a  pale  blue.  The 
colored  form  (Datura  Tatula)  has  stems  and  leaves  of  a 
brownish  color,  but  the  same  organs  are  of  a  pure  green  in 
the  white-flowering  plants  (D.  Stramonium).  Even  the 
young  seedHngs  may  be  distingu.^shed  by  the  tinge  of  color  on 
their  stem,  and  whenever  the  dark  ones  are  separated  from 
the  pale,  all  of  the  first  will  bear  blue  flowers  and  all  of  the 
latter  white. 

It  would  be  easy  to  give  a  Hst  of  such  examples,  especially 
of  garden  plants,  since  horticulturists  often  select  their  seed- 


THE   ASSOCIATION   OF   CHARACTERS  247 

lings  by  this  marl-:,  thereby  being  enabled  to  throw  out  the 
"  rogues  "  long  l^efore  the  time  (^f  blooming. 

Perennial  herbs  may  show  the  same  correlation.  In  the 
colored  forms  the  young  shoots  which  arise  from  the  root- 
stocks  have  a  dark  tinge,  but  in  the  white  varieties  they  are 
pale  or  colorless.  The  willow-leaved  \'eronica  (V.  longi- 
foUa)  affords  an  instance,  which  has  proven  useful  in  the 
study  of  the  bud-variations  of  its  hybrids.  The  hybrids  of 
this  plant  have  the  same  blue  flowers  as  the  parent  species, 
but  if  one  of  the  parents  used  for  the  cross  was  the  white 
variety,  these  blue  hybrids  are  apt  to  produce  groups  of 
white  flowers.  Such  groups  may  consist  of  a  few  corollas 
upon  a  blue  spike,  or  may  form  a  longitudinal  line,  leaving 
the  flowers  on  one  side  uncolored,  while  those  on  the  other 
are  blue.  Or  a  whole  raceme  may  be  white  on  a  plant,  whose 
remaining  spikes  are  of  the  ordinary  color.  Lastly,  a  stem 
arising  from  the  root  may  .have  returned  to  the  type  of  the 
white  parent.  In  these  latter  cases  the  color  can  be  pre- 
dicted from  the  very  first  beginning  in  the  growing  buds, 
and  the  whole  stem,  with  all  its  branches  and  leaves  will  be 
of  a  pure  green  instead  of  showing  the  brownish  tinge  of  the 
species. 

Bulbs  of  hyacinths  may  seem  to  the  layman  to  be  all 
alike,  but  the  breeder  is  often  able  to  chstinguish  their  varie- 
ties by  their  size,  the  number  of  their  little  side  bulbs,  the 
form  of  their  top,  and  especially  the  color  of  their  outer  coats. 
The  correlation  between  the  marks  of  the  dry  and  market- 
able bulbs  and  the  characters  of  the  flowers  is  so  highly 
developed  that  the  Dutch  bulb-grower  Voorhelm  is  said  to 
have  been  able  to  chstinguish  more  than  a  thousand  varieties 
of  hyacinths  solely  by  inspecting  their  bulbs. 

Another  instance  may  still  be  added.  It  relates  to  the 
association  of  the  color  in  the  bracts,  the  foHage,  and  the 
flowers  in  the  flowering  currant  (Ribes  sanguineum).     This 


248  PLANT-BREEDING 

species,  of  which  a  number  of  types  are  growing  on  the  hills 
of  California,  is  a  very  common  shrub  in  European  gardens. 
It  has  produced  a  variety  with  whitish  flowers,  which,  how- 
ever, still  betray  their  origin  by  a  pale  red  hue.  From  time 
to  time  it  returns  to  the  parent  type  in  the  way  of  bud- 
variation,  producing  Ijranches  with  dark  red  flower  spikes.  If 
now  we  compare  such  a  branch  with  the  remainder  of  the 
shrub,  we  iind  that  the  difference  is  not  limited  to  the  flowers. 
Quite  on  the  contrary,  it  shows  itself  also  in  the  bracts  and 
even  in  the  stalks  of  the  leaves.  The  bracts  are  reddish 
when  the  flowers  are  bright,  and  almost  colorless  when  the 
spikes  are  to  become  white.  At  the  first  opening  of  the  buds 
the  color  of  the  flowers  may  be  precUcted  by  this  means  for 
each  spike  of  the  variable  shrub. 

Before  leaving  the  correlations  of  organs  in  regard  to  their 
color,  I  wish  to  point  out  another  side  of  the  question,  which 
may  throw  some  light  on  the  intimate  nature  of  correlative 
changes.  The  anthocyanin  dye  is  assumed  to  be,  in  its 
chemical  composition,  related  to  the  large  group  of  tannins, 
of  which  the  common  tannic  acid  is  the  best  known  instance. 
Hence  we  may  suppose  the  existence  of  correlations  between 
the  color  and  the  taste,  or,  going  one  step  further,  between 
the  color  of  the  flower  and  the  taste  of  the  fruit  or  seeds, 
since  tannins  may  give  a  peculiar,  disagreeable,  astrin- 
gent taste,  as  is  well  known  in  the  case  of  many  unripe 
fruits. 

Such  associations  from  time  to  time  occur.  As  an  in- 
stance I  may  r^uote  a  variety  of  the  Windsor  beans(Vicia 
Faba),  newly  introduced  by  the  Dutch  seed  merchant  Van 
Namen,  in  Holland,  from  which  the  black  patches  on 
the  wings  of  the  flowers  are  absent.  Correspondingly  the 
young  seeds,  at  the  period  when  they  are  best  for  canning, 
are  of  a  paler  color  and  a  sweeter  taste  than  the  ordinary  sort. 
This  sweetness  is  caused  by  the  absence  of  the  tannin  in 


Fig.  76.     The  laciniatcd  bramble  (Riibus  Jnil'cosus  laciiiiatus)  with  divided 
petals.     B.  A  flower  of  the  ordinary  bramble. 


249 


250  PLANT-BREEDING 

their  coats.  By  this  means  the  improved  variety  may  be 
distinguished  by  the  marks  of  the  tlowers. 

Besides  their  color,  the  foHage  and  the  flowers  may  be 
correlated  in  their  form.  The  most  striking  instance  is 
that  of  those  varieties  which  have  laciniate  leaves  and 
repeat  the  same  character  in  their  petals.  Two  notable 
plants  give  proof  of  this  assertion.  One  of  them  is  the  lacin- 
iate form  of  the  ordinary  celandine,  and  the  other  a  variety 
of  the  common  bramble.  Its  petals  are  divided  into  three 
equal  lobes,  which  in  their  turn  may  show  small  incisions 
at  thcij  top.  These  are  evidently  analogous  to  the  repeated 
divisions  of  the  lobes  of  the  leaves. 

All  the  cases  liitherto  given  were  related  to  homologies 
between  flowers  and  other  organs.  But  even  within  the 
flowers  corielations  may  be  observed.  They  are  of  numer- 
ous patterns,  but  I  must  Hmit  myself  to  one  instance.  As 
such  I  choose  the  size  of  the  flowers  and  the  relative  length 
of  the  style  and  the  stamens. 

It  is  a  fact  of  daily  observation  that  many  small  flowers 
do  not  need  the  help  of  insects  for  their  fertilization.  In  a 
large  number  of  cases  their  stamens  directly  touch  the  stig- 
ma, and  the  pollen  is  spread  over  it  by  the  very  act  of  the 
opening  of  the  anthers.  ^lany  of  our  common  species  of 
the  large  family  of  the  cruciferous  plants  give  instances  of 
this.  On  the  other  hand,  great  size  in  flowers  is  often  com- 
bined with  the  production  of  stigma  and  anthers  at  such  a 
distance  that  the  pollen  can  only  reach  the  first  by  the  aid 
of  bees  and  other  visitors. 

In  the  evening  primroses,  as  in  many  other  plants,  the 
size  of  the  flowers  depends  upon  the  season  in  which  thev 
open.  This  dependence  may  go  so  far  as  to  change  the  whole 
biological  aspect  of  the  flower.  In  the  ordinar}^  sorts  of  the 
evening  primroses  (CEnothera  biennis  and  allies),  the  style 
is  short  and  the  anthers  are  arranged  around  the  stifrma. 


k  1  ^ 

^\' 

\ 

S\ 

\ 

N>j 

lH 

1 

\ 

u 

i.      ^ 

1 

Si 

^1 

A 

f 

_^ 

Fig.  77.  A.  Ordinary  celandine  {Chelidoniiim  majus).  B.  Laciniated 
celandine  (C.  w.  laciniatum),  which  originated  from  A  in  a  garden  at  Hei- 
delberg about  1590.     a  and  h.     Flowers  of  A  and  B. 


251 


252 


PLANT-BREEDING 


They  open  half  a  day  before  the  petals  expand  the  flowers 
and  invite  the  insects  to  a  visit.  During  these  last  hours, 
within  the  closed  bud  fertilization  usually  takes  place,  and 
all  is  over  before  the  insects  come,  insuring  in  this  way  a 


Fig.  78.  Flowers  of  Evening-primroses,  deprived  of  the  petals.  A. 
The  ordinary  species,  {Oen.  biennis),  a  self-pollinating  species  collected 
near  Chicago.  B.  summer-flower  of  Lamarck's  Evening-primrose,  the  stig- 
ma protruded  beyond  the  anthers.  C.  A  late  flower  of  the  same  plant 
with  the  anthers  touching  the  stigma. 

most  complete  self-fertilization.  Often  I  have  seen  the 
buds  drop  off  before  opening  without  the  least  detriment  to 
the  ripening  of  the  fruit.  In  other  cases  I  succeeded  in 
cutting  away  the  buds  about  an  hour  before  their  time  for 
opening,  but  the  young  fruits  had  already  been  fertilized 


THE   ASSOCIATION    OF    CHARACTERS  253 

and  they  ripened  quite  in  the  ordinary  way.  All  the  bright 
display  of  broad  and  sliining  petals,  of  honey,  and  a  sweet 
fragrance  is  here  absolutely  useless  and  superfluous.  Moths 
and  bees  are  attracted  in  large  numbers,  but  the  pollen 
which  they  bring  to  the  pistils  is  of  no  use  at  all. 

The  evening  primrose  of  Lamarck  widely  surpasses  its 
congeners  in  the  size  of  its  flowers.  In  connection  with 
this  difference  it  produces  styles  of  such  a  length  that  the 
stigmas  are  elevated  above  the  anthers  and  cannot  directly 
be  touched  by  their  pollen.  Here  no  fecundation  is  possible 
without  the  aid  of  the  insects,  and  if  these  are  experimentally 
excluded  the  flowers  fade  away  without  making  fruit.  All 
the  beautiful  and  ingenious  means  of  attracting  insects  come 
into  play  in  tliis  case.  No  part  of  the  flower  is  superfluous, 
as  it  is  in  the  ordinary  species. 

The  correlation  between  size  and  need  of  insect  aid, 
however,  shows  itself  as  soon  as  the  season  draws  to  its  close, 
or  rather  as  the  spikes  increase  in  length.  Towards  autumn 
the  flowers  become  steadily  smaller  and  their  styles  do  so 
too,  but  in  a  greater  degree.  The  elevation  of  the  stigmas 
above  the  anthers  decreases,  and  in  September  and  October 
they  are  touched  by  the  pollen,  insuring  by  this  means  self- 
fertiUzation  without  other  aid.  The  depositing  of  the  pol- 
len on  the  stigma  is  at  first  only  sHght  and  insufificient,  but 
as  the  summer  declines  it  steadily  becomes  more  complete, 
and  in  the  end  the  small  flowers  at  the  tops  of  the  spikes 
are  as  sure  to  fertilize  themselves  as  are  the  brightest  blos- 
soms of  the  CEn.  biennis. 

If  now  we  compare  this  case  of  correlation  with  the 
previously  mentioned  ones,  we  see  that  here  we  have  a  de- 
pendence on  external  influences,  which  causes  the  correla- 
tion to  come  into  play,  wMlst  in  the  other  instances  no  such 
excitement  was  required.  Hence  we  see  that  all  correla- 
tions are  not  of  the  same  nature.     Some  are  the  result  of 


254  PLANT-BREEDING 

the  inner  (qualities  or  characters  of  the  plant,  but  others  are 
the  product  of  reactions  to  external  stimuh. 

The  difference  observed  in  these  cases  may  be  considered 
from  a  broader  point  of  view.  Some  cases  of  correlation 
are  caused  by  characters  which  may  become  active  in  more 
than  one  organ  of  the  plant.  The  faculty  of  producing  the 
anthocyanin  dye  may  display  itself  in  flowers,  fruits,  and 
seeds,  in  stems  and  stalks,  in  leaves  and  scales,  in  one  word, 
in  almost  all  the  organs  of  the  plant.  It  is  evidently  every- 
where the  same  character,  even  where  it  sweetens  the  taste, 
by  lessening  the  amount  of  tannin.  So  it  is  with  the  lacinia- 
tion,  wliich  may  affect  leaves  and  petals.  In  all  these  cases 
the  idea  of  unit-characters  is  pressed  upon  us.  It  is  the 
assumption  that  the  same  unit  becomes  active  in  the  dif- 
ferent parts  of  the  same  organism. 

In  the  other  cases  different  ([uaUties  may  depend  in  the 
same  manner  upon  the  changes  of  the  environmental  con- 
ditions of  life.  If  these  are  favorable  all  will  increase,  but 
under  adverse  influences  they  will  decrease  together.  In 
this  way  different  unit-characters  may  be  correlated  but 
the  relation  is  more  in  the  nature  of  accidental  coincidence 
than  of  actual  identity. 

All  in  all,  the  study  of  these  correlations  is  of  the  highest 
interest,  as  well  for  science  as  for  practice.  By  means  of 
them  we  may  predict  one  quaUty  or  one  function  from  the 
study  of  others.  Insigniflcant  characters  or  organs  may 
show  us  the  way  and  guide  us  in  our  selection.  The  more 
we  familiarize  ourselves  with  such  seemingly  subordinate 
marks,  and  with  their  relation  to  the  quaUties,  which  deter- 
mine the  commercial  worth  of  the  plant  or  of  the  harvest, 
the  better  we  shall  be  prepared  for  the  work  of  selection. 
To  judge  quinces  from  their  seedlings,  as  Burbank  did, 
may  seem  incredible  to  those  who  are  not  initiated  into 
the  mystery  of  this  principle,  but  it  can  be  learned,  either 


THE   ASSOCIATION   OF   CHARACTERS  255 

in  practice  or  on  the  basis  of  our  general  conceptions  of 
association  of  characters. 

B.  CORRELATIONS  IN  AGRICULTURAL  BREEDING 
It  seems  hardly  necessary  to  repeat  the  evidence  given 
in  the  former  chapter.  We  may  at  once  go  into  the  details 
and  consider  those  cases,  in  which  the  correlations  give 
direct  indications  of  valuable  qualities  to  the  agricultural 
breeder.  Of  course  the  application  of  the  principle  of 
correlation  to  the  practice  of  selection  means  the  judging  of 
the  worth  of  single  plants  on  the  ground  of  seemingly  in- 
significant marks. 

As  a  first  instance  I  choose  the  peas,  which  have  been 
studied  from  this  point  of  view  by  Tedin.  Peas,  as  they 
are  commonly  cultivated,  are  considered  as  belonging  to 
two  nearly  alUed  botanical  species,  Pisum  arvense  and 
Pisum  sativum.  In  reaUty  they  consist  of  numerous  ele- 
mentary species,  which  are  quite  distinct  from  one  another. 
More  than  a  hundred  types  may  be  distinguished  by  the 
color  of  the  flowers  and  of  the  seeds,  by  the  number  of  the 
kernels  in  the  pod,  by  the  cHsposition  of  the  flowers  along 
the  axis,  whether  sohtary  or  placed  in  pairs,  by  the  character 
of  the  ramification  of  the  stem,  and  by  numerous  other  sub- 
ordinate marks.  Each  of  these  qualities  proves  to  be  con- 
stant in  pure  cultures,  and  each  is  correlated  to  some  feature 
which  may  be  of  influence  on  the  harvest.  Among  them  the 
time  of  the  beginning  of  the  flowering  period  is  related  to  the 
period  of  the  ripening  of  the  seeds  in  so  simple  a  way,  that 
it  may  easily  be  understood,  and  that  we  only  wonder  how 
it  has  been  possible  that  it  has  not  previously  been  discovered. 
Some  individual  plants  produce  their  first  flower  in  the  axil 
of  one  of  the  lower  leaves  of  the  stem,  but  others  are  bare  of 
flowers  over  a  notable  length.  Now  it  would  seem  that  this 
was  only  a  case  of  fluctuating  variability,  the  length  of  time 


256  PLANT-BREEDING 

required  for  the  beginning  of  the  blooming  period  varying  in 
the  different  individuals.  If  tliis  were  so,  the  character  would 
only  be  of  slight  value,  and,  in  the  main,  dependent  on  ma- 
nure and  culture.  But  Tedin  found  that  there  are  a  number 
of  types,  differing  from  each  other  in  the  age  in  wliich  they 
begin  to  flower,  and  that  each  is  constant,  when  propagated 
from  pure  seed.  Moreover  he  observed  that  the  early- iiower- 
ing  plants  are  early  in  ripening  their  seeds  too,  while  the 
late-flowering  individuals  bring  their  harvest  only  in  the 
latter  part  of  the  season.  That  this  would  hold  good  for 
the  first  pods,  might  be  expected,  but  the  observation  showed 
that  the  rule  is  applicable  to  the  whole  harvest. 

Earliness  of  ripening  often  is  a  most  prevaiHng  point  in 
the  determination  of  the  cultural  worth  of  a  variety.  The 
influence  of  unfavorable  weather,  such  as  often  occurs  in 
the  latter  part  of  the  summer,  is  thereby  eliminated.  Heavy 
rains  may  bring  the  necessity  of  harvesting  in  a  moist  con- 
dition. Warm  and  damp  weather  without  sunshine  may 
induce  the  plants  to  produce  a  rich  foliage  consuming  the 
nutriment  for  the  pods  and  thus  deteriorating  them.  Cold 
days  protract  the  process  of  ripening  and  thus  prolong  the 
exposure  to  insect  pests.  All  kinds  of  dangers  speak  in 
favor  of  the  cultivation  of  early  varieties. 

Such  may  now  be  secured  by  the  correlated  mark  of 
the  place  of  the  first  flower  on  the  stem.  On  the  ground  of 
this  mark  promising  plants  are  selected  and  isolated  in 
order  to  determine  their  worth  afterwards,  in  their  own 
harvest  and  in  that  of  their  progeny. 

Apples  and  pears  may  give  a  second  instance.  In  the 
first  half  of  the  last  century  the  Belgian  horticulturist  Van 
Mons  discovered  the  significance  of  their  numerous  elemen- 
tary species  and  the  relation  between  their  fruits  and  the 
form  and  growth  of  their  fohage  and  branching.  Since  his 
time  much  has  been  done  for  the  amelioration  of  these  im- 


THE   ASSOCIATION   OF   CHARACTERS  257 

portant  trees,  and  numberless  new  varieties  have  been  pro- 
duced. Among  them,  more  than  once  it  has  been  the  aim 
of  the  breeder  to  obtain  seedless  fruits,  and  shortly  after 
the  time  of  \'an  Mons  some  such  types  have  been  propagated 
and  introduced  into  trade,  but  without  any  noticeable  suc- 
cess. In  European  gardens,  here  and  there,  and  not  even 
rarely,  some  old  tree  is  still  testifying  of  these  attempts.  They 
belong  to  more  than  one  variety,  as  for  instance  the  "Berga- 
mottc  sans  pepins"  and  "Riha's  Kernlose  Butterbirne." 
But  as  yet  no  breeder  has  succeeded  in  combining  the  lack 
of  seeds  with  other  desirable  quahties.  Of  late,  in  America, 
the  Spencer  Seedless  Apple  Company  at  Grand  Junction, 
Colorado,  promises  to  introduce  a  new  and  better  seedless 
variety  of  apples. 

Now  the  lack  of  seeds  is  directly  correlated  with  some 
other  valuable  equalities.  In  the  first  place  not  only  the 
kernels  arc  absent,  but  also  the  core,  and  the  whole  heart 
of  the  fruit  consists  of  succulent  and  eatable  tissue.  No 
labor  has  to  be  spent  in  boring  out  the  core,  w^ien  preparing 
the  apples  for  conservation,  and  no  useless  parts  heighten 
the  freight  in  shipping.  These,  however,  are  not  the  most 
important  quahties  of  seedless  fruits.  Quite  on  the  contrary, 
the  relation  of  the  seeds  to  the  nourishment  of  the  tree  is 
preponderating.  The  seeds  contain  the  germ  of  a  new  tree, 
and  the  nutriment  necessary  for  its  first  development.  For 
a  large  part  this  consists  of  albuminous  substances  and  their 
production  exhausts  the  tree  to  a  much  higher  degree  than 
the  many  times  more  voluminous,  but  only  sugary  tissues  of 
the  whole  apple.  Seedless  trees,  therefore,  are  much  less 
exhausted  by  their  fruits  than  orchnary  varieties.  Their 
harvest  will  be  larger  with  the  same  consumption  of  manure 
or  with  the  same  extension  of  the  fohage  and  roots,  which 
absorb  the  nourishment  and  prepare  and  send  it  to  the  fruit. 
Experience  has  shown  the  high  significance  of  tliis  relation 


258  PLANT-BREEDING 

for  the  oranges  of  southern  California  and  many  other  kinds 
of  fruit-trees,  and  we  may  confidently  assume  that  the  same 
rule  will  prevail  for  all  other  trees. 

Among  agricultural  plants  instances  of  observed  cor- 
relations arc  very  numerous.  In  potatoes  richness  of  flowers 
indicates  a  late  ripening  of  the  tubers,  an  abundance  of 
seed-berries  is  related  to  a  smaller  production  of  potatoes, 
and  in  the  same  way  the  extension  of  the  foUage,  the  number, 
height  and  branching  of  the  stems  and  some  other  marks 
may  be  used  in  predicting  the  ciuahties  of  the  harvest.  Flax 
may  be  judged  by  its  stalks.  Long  and  thick  stems,  nu- 
merous side-branches,  and  numerous  pods  are  assumed  to 
be  indicative  of  strong  development  and  long  and  sohd 
fibers.  In  hops  the  late  kinds  are  richer  in  resinous  sub- 
stances, but  theii  aroma  is  not  so  fine  as  in  the  earlier  .sorts 
and  the  botanical  marks  of  the  hop-ljells,  such  as  hairiness, 
length  of  the  axis  between  the  succeeding  bracts,  and  many 
others  may  be  made  use  of  in  judging  the  value  of  the  differ- 
ent varieties.  Clovers  are  very  rich  in  elementary  species, 
which  may  be  discerned  by  the  form  of  the  leaves,  by  the 
presence  or  absence  of  whitish  spots  on  the  leaflets,  by  the 
size  and  the  color  of  the  seeds  and  by  some  other  marks, 
correlated  with  the  practical  c^uaUties  of  the  types  under 
consideration.  \'arieties  of  vetches  (Vicia)  in  which  the 
stems  begin  to  branch  at  a  short  distance  from  the  root  are 
less  sensible  to  frosts  and  bad  weather  during  winter  than 
those  which  remain  unbranched  for  a  longer  period.  Nu- 
merous other  instances  could  be  given,  showing  the  interest 
attached  to  a  thorough  study  of  apparently  insignificant 
marks  and  even  of  such  differentiations  as  escape  the  atten- 
tion of  the  ordinary  observer. 

Instead  of  prolonging  the  Hst,  however,  I  prefer  to  call 
attention  to  some  cases  of  especial  interest,  in  which  the 
correlations  mav  be  more  or  less  clearlv  understood.     One 


THE   ASSOCIATION   OF    CHARACTERS  259 

of  the  most  prominent  features  in  the  value  of  agricultural 
products  is  found  in  the  size  of  the  seeds,  or  as  it  is  often 
stated,  in  the  number  of  seeds  wanted  to  fill  a  Utcr.  Larger 
seeds  are  as  a  rule  preferred,  and  many  regions  which  are 
renowned  all  over  the  world  for  the  superiority  of  their 
seed  grains,  owe  this  repute  in  a  high  degree  to  their  care 
in  sifting  the  seeds  and  separating  the  biggest  ones  as  well 
for  the  continuance  of  their  race  as  for  sale.  It  is  interest- 
ing to  look  into  the  reasons  for  this  preferment.  In  the  first 
place  comes  the  relation  between  the  useless  and  the  useful 
parts  of  each  single  kernel.  In  a  seed  the  inner  or  nutritious 
tissues  are  surrounded  and  protected  by  the  outer  layers 
or  integuments.  The  inner  parts  may  consist  of  the  germ 
alone,  or  of  the  germ  and  the  albumen,  the  germ  containing 
chiefly  the  albuminous  and  oily  substances,  and  the  albu- 
men being  orchnarily  the  tissue  in  which  the  starch  is  the 
most  prominent  nutritive  element.  The  integuments  or 
outer  layers  are  not  only  devoid  of  nutritious  contents,  but 
are  also  ordinarily  of  a  considerable  firmness.  They  are 
built  up  of  different  tissues.  In  the  seeds  of  the  clover  the 
external  layer  is  cuticularized.  These  coverings  have  their 
significance  for  the  protection  of  the  germ  against  all  kinds 
of  obnoxities,  but  considered  in  the  harvest  they  evidently 
diminish  the  quantity  of  nutrient  parts  pro  unit  of  weight. 
Hence  the  conclusion  that  the  nourishing  value  of  a  given 
quantity  of  corn,  of  grain,  of  peas,  or  of  any  other  eatable 
kind  of  seed,  depends  in  a  high  degree  on  the  development  of 
those  integuments.  The  thicker  they  arc,  the  lesser  is  the 
part  of  the  useful  tissues,  while  seeds  with  thinner  shells 
contain  more  nutritive  parts,  and  moreover  are  more  easily 
digestible. 

Therefore  the  breeder  always  has  to  select  the  plants 
with  thinly  covered  seeds,  and  the  correlation  which  exists 
between  this  quality  and  the  size  of  the  seeds  is  his  easiest 


26o  PLANT-BREEDING 

and  most  reliable  guide.  For  numerous  determinations 
have  taught,  that  large  seeds  have  thinner  integuments  than 
smaller  ones.  Tliis  rule  holds  good  for  grains  and  peas 
and  probably  for  all  agricultural  crops,  and  even  for  flowers 
and  wild  plants  the  same  relations  prevail.  The  size  of  the 
germ  and  albumen  and  the  development  of  the  surrounding 
layers  are  evidently  dependent  on  the  same  influences. 
Individual  strength  of  the  variety,  or  a  better  nourishment 
of  the  single  jjlants  will  cause  both  of  them  to  increase. 
But  the  measure  of  the  increment  will  be  different  for  them, 
and  therefore  their  proportion  in  weight  and  volume  will 
be  affected  by  the  change.  The  relation  is  the  same  as  that 
which  we  have  studied  in  our  last  chapter  for  the  size  of 
the  flowers  and  the  length  of  the  styles  in  the  evening  prim- 
roses. Or,  in  other  words,  favorable  conditions  will  promote 
the  development  of  the  inner  nutritive  parts  of  the  seeds  in 
a  higher  measure  than  that  of  the  less  digestible  coverings. 
The  preference  commonly  given  to  large  seeds  may  be 
explained  by  the  evidence  afforded.  But  the  detailed  cor- 
relation is  not  the  only  one.  On  the  contrary,  the  size  of 
the  seed  is  correlated  with  its  development  during  the  ger- 
minating period,  and,  through  this,  has  an  influence  on  the 
individual  strength  and  size  of  the  whole  plant.  Moreover, 
larger  seeds  are  known  to  be  more  equal  in  size,  the  smaller 
specimens  which  are  so  common  in  non-selected  samples, 
faihng  in  them.  This  conformity  results  in  simultaneousness 
of  germination  and  development,  two  of  the  weightiest  factors 
for  a  regular  growth  of  the  crop.  Especially  they  determine 
whether  at  the  time  of  the  harvest  all  ears  or  all  pods  wifl  be 
duly  ripe,  or  whether  a  larger  or  lesser  part  of  them  will  be 
lost.  Ripening  too  early,  an  ear  may  lose  its  kernels  before 
the  harvest,  whilst  ripening  too  late  it  is  of  no  use  at  all. 
A  simultaneous  development,  therefore,  is  one  of  the  most 
desirable  qualities  in  cultivated  plants,   and  this  may  be 


THE   ASSOCIATION   OF   CHARACTERS  261 

reached  by  selecting  on  the  ground  of  seeds  of  ecjual  size,  or 
simply  on  the  base  of  choosing  the  largest  seeds.  Apart 
from  these  general  correlations  there  are  two  minor  points, 
for  which  I  might  call  your  attention.  The  first  is  indicated 
by  the  common  proverb : 

One  year's  seed 
Is  seven  years'  weed. 
It  means,  that  a  large  number  of  weeds  and  other  wild 
plants  produce  seeds,  only  a  part  of  which  will  germinate 
in  the  next  spring.  Another  part  will  sleep  in  the  soil  and 
only  be  awakened  in  the  spring  of  the  following  year,  whilst 
the  more  resistant  kernels  will  stand  two  or  more  years  and 
come  into  germination  after  this  prolonged  period  of  rest. 
Some  spare  seeds  may  even  rest  as  long  as  six  or  seven  years ; 
whence  the  saying  quoted.  This  rule  is  not  at  all  limited 
to  weeds,  but  embraces  the  different  sorts  of  clover  and  of 
other  allied  leguminous  forage  plants. 

Now,  here  also,  we  observe  a  correlation  between  the 
size  of  the  seeds  and  the  time  rec^uired  for  their  germination. 
As  a  rule,  the  smaller  seeds  have  the  thickest  and  hardest 
coats,  as  we  have  already  seen,  and  it  is  exactly  the  extreme 
resistance  of  the  coats,  which  causes  them  to  lie  dormant 
for  so  long  a  time.  If  we  sow  seeds  of  common  clover  or 
of  the  crimson  species  (Trifolium  incarnatum)  on  a  layer 
of  moist  blotting  paper,  we  can  easily  pick  out  day  after  day 
those  which  produce  their  rootlet.  In  the  main  the  larger 
seeds  will  thus  be  seen  to  germinate  first,  and  after  a  week 
or  more  only  the  small  kernels  remain.  Among  these, 
some  will  germinate  during  the  next  weeks,  but  some  spare 
ones  will  remain  dormant  until  the  next  year. 

Evidently  it  is  of  high  practical  interest,  in  the  first  place, 
to  have  all  or  nearly  all  the  seeds  of  a  sowing  germinating 
in  the  same  spring,  and  in  the  second  place  to  have  them  all 
coming  up  in  the  same  week  or  at  least  as  nearly  at  the  same 


262  PLANT-BREEDING 

time  as  possible.  Varieties  with  larger  seeds  are  therefore 
preferable  by  far,  since  they  do  not  contain  the  aberrant 
little  ones,  which  are  the  chief  cause  of  the  loss  and  of  the 
trouble. 

At  the  SwecUsh  agricultural  experiment  station  at  Svalof 
another  method  has  been  developed  to  get  rid  of  this  nui- 
sance. Though  it  is  not  directly  related  to  our  main  subject, 
it  is  as  well  to  dwell  upon  it  here,  for  a  short  time.  It  has 
been  discovered  that  with  clover  and  other  leguminous  forage 
crops  the  whole  rjuestion  of  the  sluggishness  of  the  germinat- 
ing process  is  due  to  the  resistance  of  the  outermost  layer 
of  the  seed  coats  to  the  absorption  of  water.  Small  seeds 
of  clover  remain  absolutely  dry  in  water  for  days  and  weeks, 
and  in  this  condition  they  may  even  be  thrown  into  boiling 
water  without  being  killed.  It  is  the  very  thin  cuticle  of 
their  epidermis  which  impedes  the  penetrating  of  the  water 
into  the  inner  parts  and  thus  prevents  the  initiation  of  that 
process  of  saturation  which  is  the  necessary  condition  of  all 
germination.  If  there  were  only  a  small  hole,  or  a  small 
non-resistant  spot,  the  water  might  pass  by  this  and  effect 
a  complete  imbiljition.  ( )n  this  principle  the  Svalof  method 
is  based.  It  allows  of  filing  all  the  seeds  on  a  small  spot, 
making  their  coats  locally  permeable  for  water,  without 
changing  them  in  any  other  way.  In  order  to  do  this,  an 
apparatus  has  been  built,  which  throws  the  seed  against  a 
filing  disk  in  an  obhc^ue  direction  and  in  continuous  current. 
Thereby  the  culture  of  many  species  of  leguminous  plants 
has  been  made  possible  and  advantageous,  which  formerly 
were  disregarded  on  account  of  their  imperfect  germination. 
Bv  this  means  the  selection  of  larger  seeds  and  the  applica- 
tion of  this  part  of  the  principle  of  correlation  is  made  super- 
fluous. 

My  second  point  is  the  value  of  rapidly  germinating 
seeds  in  all  cases  where  the  germination  period  is  the  time 


Fig.    79.     Panicles    of    oats.     A.  With    erect,     and    B.  With     spreading 

branches. 

263 


264  PLANT-BREEDING 

for  the  attacks  of  some  dreaded  disease.  For  the  sooner  the 
time  of  scnsibihty  is  over,  the  smaller  will  be  the  harm 
and  the  larger  the  number  of  uninjured  thriving  plants. 
Experiments  have  been  made  in  tliis  direction  in  Sweden 
on  the  resistance  of  grains  against  the  devastations  of  the 
frit-fly  (Oscinis  frit).  This  is  a  little  black  insect,  attaining 
a  length  of  only  2  or  3  mm.  and  easily  recognizable  by  its 
metallic  brightness,  black  legs,  and  yellow  feet.  It  invades 
the  grains  chiefly  during  the  germination  period,  depositing 
its  eggs  on  the  young  plants.  The  larvae  creep  along  the 
leaves  and  their  sheaths  downward  until  they  reach  the  young 
halms,  and  in  eating  these  they  destroy  the  germ  of  all  further 
dcA'clopment.  Some  of  the  seedUngs  may  die  shortly  after- 
wards, others  may  show  signs  of  life  during  some  time,  but 
their  growth  is  abnormal  and  for  the  harATSt  they  are  wholly 
lost.  Whole  fields  of  all  kinds  of  cereals  may  be  destroyed 
by  this  calamity  during  some  few  weeks. 

One  of  the  best  means  against  the  attack  of  these  flies  is 
the  passing  of  the  dangerous  period  of  life  as  rapidly  as 
possible.  As  soon  as  the  young  halms  are  old  enough  to 
resist  the  invasion,  the  insects  become  nearly  harmless.  On 
the  basis  of  our  considerations  concerning  the  correlation 
of  the  size  of  the  seeds  with  the  rapidity  and  simultaneous- 
ness  of  the  germination,  we  may  therefore  expect  that  the 
sowing  of  selected  large  seeds  or  of  large-seeded  varieties 
will  give  the  desired  protection.  This  is  exactly  the  result 
of  the  Swedish  experiments.  Nilsson  and  his  staff  made 
comparative  sowings  of  large  and  of  small  seeds  separated 
from  one  another  by  sifting,  or  even  by  simply  choosing  the 
upper  kernels  of  each  spikelet  for  one  trial,  and  the  under 
kernels,  which  as  a  rule  arc  larger,  for  the  other.  By  this 
method  all  varietal  differences  were  excluded  and  the  result 
was  for  oats,  that  the  loss  from  the  attacks  of  the  fly  was 
small  for  the  large  seeds,  but  very  notable  among  the  smaller, 


THE   ASSOCIATION   OF   CHARACTERS  265 

and  therefore  more  slowly  and  more  irregularly  germinating 
kernels. 

As  we  have  already  seen,  correlations  may  be  cUvided 
into  those,  which  arc  easily  traceable  to  a  common  cause, 
and  those  in  which  the  causal  relation  of  the  single  phenom- 
ena remains  obscure.  In  the  adduced  example  of  the  seeds 
this  relation  is  evident,  at  least  to  some  extent,  and  therefore 
I  will  now  choose  a  case  in  which  there  is  no  obvious  reason 
for  the  connected  c^uaHties  to  be  so  connected.  Our  appre- 
ciation of  the  correlation  can  in  such  cases  only  be  based 
on  direct  observation.  This  however,  requires  a  most 
minute  study,  on  one  side  of  seemingly  insignificant  botani- 
cal characters,  and  on  the  other  of  the  industrial  qualities 
of  the  plant. 

Among  the  grains  the  panicles  of  the  oats  give  the  best 
evidence.  Their  shape  and  mode  of  brandling  are  variable 
to  a  high  degree.  The  branches  are  combined  into  whorls. 
The  number  and  relative  development  of  these  branches 
proves  to  be  constant  for  each  pure  type.  The  apparent 
high  variabihty  is  to  be  reduced  to  a  large  group  of  single 
forms,  which  when  considered  for  themselves  are  narrowly 
circumscribed  and  do  not  transgress  their  differentiating 
hmits.  Some  panicles  have  their  largest  branches  longer 
than  the  main  axis,  in  others  they  are  shorter.  Those  of 
the  first  group  are  ordinarily  stiff  and  dense,  those  of  the 
second  being  more  flaccid  and  more  widely  spread.  The 
biggest  kernels  may  be  found  in  the  lower  spikelets,  or  they 
may  prefer  the  middle  and  upper  ones,  and  experience  has 
shown  that  only  such  sorts  are  commendable  which  have 
their  biggest  seeds  above  the  middle. 

Most  reliable  marks  are  given  by  the  color  of  the  seeds. 
The  sHghtest  differences  in  tint  are  wholly  constant  and 
indicative  of  corresponding  practical  quaUtics  of  the  sorts. 
Yellow  and  yellowish,  straw  and  reddish-yellow,  whitish  and 


^^^^^^^^^^^^^^^^^^^^^■V'' *- 

!■ 

^^^^^^^^^^HT  ^v  .^^^B^U 

I^^l 

^^^B^vBSi 

K^^^^^^l 

■MHH 

^^^^v» '"I^Bk^^K 

^^^^Kt^'^^Eiu^H 

Iftl^l 

■n^BH 

^H^IkIS^^h 

K/JaP-^^l 

^^^,1^9^H 

^^KV^H 

^^^^^^_^             ^^^^1 

H 

Fig.  80.  Svalof  Grenadier  wheat,  the  best  of  the 
new  Swedish  varieties  of  wheat,  very  producti\-e  of 
grain  and  straw. 

266 


P'ig.  Si.     Svalof  Borc-whcat,  a  new  hardy  variety  for  the 
cultures  of  middle  Sweden. 

267 


268  PLANT-BREEDING 

grayish-yellow  tinges,  half  a  dozen  of  shades  of  brown,  and 
more  of  less  completely  black  types  may  be  distinguished. 
Some  of  them  have  given  proof  of  being  suitable  for  some 
regions  and  some  uses,  while  others  are  preferable  under 
other  conditions. 

The  spikelets  may  contain  one,  two,  or  three  flowers,  and 
these  numljers  arc  dispersed  on  the  different  branches  of 
the  panicle  according  to  the  special  properties  of  the  sorts 
under  consideration.  Spikelets  with  two  flowers  are  as  a 
rule  preferable,  since  there  is  a  near  relation  between  this 
number  and  the  size  of  the  kernels.  In  each  spikelet  the 
flower  of  the  undermost  palet  always  gives  the  biggest  kernel. 
If  it  is  the  only  one  it  may  be  small,  but  as  soon  as  it  becomes 
accompanied  by  a  second  or  a  third  flowering  scale,  its  kernel 
becomes  heavier.  In  this  way  the  many-flowered  spikelets 
do  not  only  give  more  kernels  but  also  bigger  ones,  and  with 
them  all  the  advantages  we  have  described  of  large  seeds. 
The  size  of  the  empty  scales  at  the  top  of  the  axis  of  the 
spikelet,  the  little  hairs  at  the  base  of  the  palets,  the  more 
or  less  twisted  awns  and  their  curvature  give  many  mor- 
phological marks,  whose  correlation  with  the  breeding 
quahties  may  be  studied. 

Corresponding  marks  are  afforded  by  wheat,  and  rye, 
and  barley.  Among  them  the  number  of  the  kernels  in  each 
spikelet  prevails,  but  the  size  and  density  of  the  whole  ear, 
the  characters  of  the  outer  scales,  and  even  their  hairiness 
may  be  advantageously  compared.  At  the  Swedish  agri- 
cultural experiment  station,  for  each  genus  of  cereals  a  system 
of  classification  has  been  traced  which  gives  a  survey  over 
all  these  botanical  marks  and  their  relation  to  industrial 
quahties.  These  relations  of  course  have  had  to  be  studied 
experimentally,  and  large  cultures  as  well  as  exact  measure- 
ments and  determinations  of  chemical  value,  baking  and 
brewing  qualities  and  many   others  have  been    made.     It 


THE   ASSOCIATION    OF   CHARACTERS  269 

has  taken  years  to  arrive  at  a  sufficient  degree  of  knowledge 
of  all  these  correlations,  and  the  investigations,  though  cov- 
ering more  than  ten  years,  have  as  yet  not  nearly  been 
exhausted.  But  the  general  result  has  been  that  the  indus- 
trial worth  of  any  incUvidual  plant  can  now  be  estimated  by  a 
thorough  inspection  of  its  panicles  or  ears  and  with  a  degree 
of  certainty  which  is  wholly  sufficient  for  all  purposes  of 
selection. 

As  an  illustration  of  the  high  significance  of  these  corre- 
lations, I  will  now  return  to  the  example  of  the  Primus-barley, 
of  which  I  spoke  in  a  previous  lecture.  As  already  pointed 
out,  all  endeavors  to  breed  a  race  of  Chevaher-barley  with 
stiff  culms  had  led  to  no  appreciable  ameHoration,  and 
the  cultures  in  this  direction  had  to  be  given  up.  The 
principle  of  correlation,  however,  pointed  to  another  way 
of  solving  the  problem.  Instead  of  trying  to  breed  a  Cheva- 
lier-barley with  rigid  halms,  a  stift"  variety  was  chosen,  and 
it  was  proposed  to  give  to  this  the  quahties  of  a  fine  brewer's 
barley.  In  Sweden  a  kind  of  barley  is  largely  cultivated 
which  bears  the  name  of  Imperial  barley  and  belongs  to 
the  subspecies  of  Hordeum  ercctum  with  stift"  culms,  hairy 
scales,  and  coarse  kernels.  This  variety,  the  good  quahties 
of  which  were  duly  appreciated,  was  taken  for  a  starting- 
point  in  order  to  produce  the  desired  barley  for  the  brewers. 
The  study  of  the  correlations  between  morphological  and 
industrial  features  had  led  to  the  discovery  of  a  coincidence 
of  some  marks  of  the  hairs  on  the  base  of  the  scales  vvdth  the 
composition  of  the  albumen  of  the  grains.  Long  and 
straight  ones  are  correlated  with  coarse  kernels,  but  short 
and  crisp,  more  or  less  woolly  hairs  are  indicative  of  those 
c^uahties  which  stamp  a  barley  as  a  good  kind  for  the 
brewery. 

On  the  basis  of  this  correlation,  combined  with  the  dis- 
covery of  the  existence  of  innumerable  individual  variations,  it 


270  PLANT-BREEDING 

was  judged  probable  that  among  the  resistant  Imperial  barley 
some  spare  individuals  might  l3e  found  with  compact  kernels, 
suitable  for  brewery  purposes,  and  that  they  would  be  recog- 
nizable by  the  form  of  the  hairs  of  their  scales.  This  con- 
clusion led  to  a  formal  hunt  for  such  specimens.  Of  course, 
among  some  hundreds  they  could  hardly  be  expected,  but 
in  each  thousand  it  might  be  possible  to  find  a  single  one. 
All  the  fields  of  the  Imperial  barley  of  the  station  were 
scru])ulously  inspected,  and  any  specimen  with  a  diverging 
type  of  hairiness  was  marked  out.  '  Many  thousands  of  plants 
with  long  and  straight  hairs  had  to  be  analyzed  before  the 
desired  ones  could  be  found.  At  the  end  some  sixty  were 
judged  worthy  of  further  trial.  Their  ears  were  collected 
separately,  and  in  the  next  season  the  progeny  of  each  single 
selected  mother  plant  could  be  studied.  The  investigation 
was  now  directly  turned  to  the  brewery  qualities  and  taught 
that  in  some  thirty  of  the  cultures  the  expected  correlation 
was  really  present. 

This  result  crowned  the  labor  of  the  previous  summer, 
as  well  as  it  gave  proof  of  the  rehability  of  the  principle  in- 
volved. It  was  quite  sufficient  for  the  practical  aim  of  the 
experiment.  On  the  field  plots  of  this  second  generation 
eight  new  and  valuable  types  could  be  chscerned,  each  of 
them  evidently  a  fine  brewer's  barley  with  resistant  halms. 
They  were  quite  as  good  as  the  ordinary  cultivated  Chevalier 
sorts,  though  not  at  all  derived  from  them.  Among  them 
all  further  care  had  to  be  directed  to  a  rapid  propagation, 
and  to  comparative  trials  of  the  eight  elite  strains.  One 
of  them  was  found  to  be  the  best,  and  to  comply  with  all 
the  demands  of  the  brewers.  It  got  the  name  of  Primus- 
barley,  as  already  c^uoted.  It  was  resistant  even  on  the 
hardest  soils  of  Middle  Sweden,  but  its  kernels  can  scarcely 
be  distinguished  from  those  of  the  best  Chevalier  varieties. 
It  is  a  brewery  barley  of  the  very  first  rank,  on  account  of  its 


THE   ASSOCIATION   OF   CHARACTERS  271 

pale  yellow  color,  its  smooth  and  downy  coat,  its  typical 
form,  and  the  chemical  quahties  of  its  tissues. 

This  new  race  has  been  constant  and  uniform  from  the 
very  first  moment  of  the  discovery  of  its  mother  plant.  Its 
progeny  had  only  to  be  multipUed,  absolutely  no  selection 
being  wanted.  The  multiphcation  has  been  very  rapid,  and 
nine  years  after  its  commencement  (1892)  it  could  be  given 
into  trade  (1901),  having  triumphed  at  numerous  agricul- 
tural expositions  over  all  other  similar  sorts. 

Apart  from  the  enormous  amount  of  work  involved,  as 
well  in  the  selection  of  the  first  year  as  in  the  consecutive 
comparative  trials  of  the  originally  isolated  strains,  this  great 
success  is  in  the  main  due  to  the  disco^'ery  of  the  laws  of 
variabiUty  and  correlation  governing  the  characters  of  our 
cereals.  It  is  a  principle,  which  already  has  given  proof 
of  its  wide  apphcabiUty  to  nearly  all  the  large  agricultural 
crops,  embracing  even  the  minor  types,  such  as  vetches  and 
other  leguminous  forage  plants.  It  is  a  leading  idea,  and 
hardly  any  hmits  seem  to  be  set  to  its  influence.  To  the 
practical  breeder  it  shows  the  way  in  nearly  all  the  burning 
questions,  and  for  the  scientist  it  may  prove  to  give  the 
solution  of  numerous  problems  which  have  eluded  his  evo- 
lutionary speculations  for  more  than  half  a  century. 

C.  A  METHODICAL  STUDY  OF  CORRELATIONS 
Correlations  between  botanical  marks  and  breeding  qual- 
ities are  to  be  considered  as  rehable  guides  in  the  work  of 
selection.  Numerous  instances  have  been  dealt  with  in 
which  single  inchviduals,  chosen  in  a  field  on  account  of 
some  slight  deviation  of  form,  color,  or  hairiness,  have 
become  the  parents  of  valuable  varieties.  Until  some  years 
ago  our  knowledge  of  these  correlations  was  Hmited  to  a 
greater  or  lesser  number  of  isolated  cases,  and  although 
their  significance  was  clear  enough,  it  was  hardly  possible 


272  PLANT-BREEDINCx 

to  point  out  the  way  in  which  further  progress  might  be 
attained. 

At  the  Swedish  agricultural  experiment  station  of  Svalof, 
however,  it  soon  became  evident,  that  this  principle  might 
some  day  become  the  basis  of  exact  methodical  work.  The 
fact  once  ascertained,  that  the  fields  of  our  orchnary  crops 
are  by  no  means  uniform,  and  moreover  conceal  a  noticeable 
number  of  excellent  types,  suitable  for  the  most  widely 
different  reciuircments,  the  need  was  instantly  felt  for  a 
method  which  would  enable  the  breeder  to  make  liis  selec- 
tions as  large  and  as  profitable  as  possible.  According  to 
the  rules  already  explained,  this  choice  must  always  be  a 
two-fold  one.  In  the  first  place  comes  the  work  in  the 
ordinary  fields,  the  picking  out  of  the  aberrant  individuals 
which  seem  to  promise  some  special  result.  Thousands  of 
ears  are  inspected  and  tested,  and  on  account  of  certain 
marks  those  are  chosen  which  do  not  comply  with  the  main 
type.  Then  their  seeds  are  sown,  and  the  progeny  of  each 
single  specimen  is  studied  and  compared  with  the  already 
cultivated  varieties.  This  comparison  depends  in  part  on 
the  same  marks  as  the  initial  choice  and  in  part  on  the 
direct  control  of  the  agricultural  ciuahties.  By  means  of 
this  latter  the  judgment  is  finally  made  independent  of  the 
laws  of  correlation,  which  by  this  contrivance  afford  only 
the  means  to  reach  the  aim  by  a  far  shorter  and  easier 
way  than  would  be  possible  if  the  first  choice  itself  had  to 
be  made  on  the  basis  of  exact  measurements  of  the  practical 
value  of  the  individual  plants. 

We  thus  see  that  we  may  limit  our  study  to  the  initial 
choice.  "We  may  leave  the  subsequent  work  out  of  consider- 
ation, since,  as  far  as  the  correlations  are  concerned,  they 
require  the  appreciation  of  quite  the  same  marks.  But  in 
order  to  make  the  first  choice  as  reliable  and  as  profitable 
as  possible,   a  thorough  knowledge  is  required.     It  must 


Fig.  82.     A  panicle   of  oats   with   weak   branches,    photo- 
graphed at  Svalof,  Sweden. 


274  PLANT-BREEDING 

include  three  subdivisions.  These  have  to  deal  respectively 
with  the  morphological  marks,  with  the  agricultural  quaUties, 
and  with  the  correlations  between  these  two  groups.  The 
agricultural  qualities  may  be  assumed  to  be  manifest,  but 
the  botanical  pecuharitics  have  hitherto  been  neglected,  or 
studied  only  in  a  superficial  way,  so  far  as  their  appreciation 
was  needed  for  the  ordinary  botanical  systems. 

These  older  systems  were  based  on  a  very  imperfect 
knowledge  of  the  real  nature  of  the  variabihty.  No  sowings 
had  been  made  in  order  to  study  this  phenomenon,  and  it 
was  simply  assumed  that  all  minor  pecuharitics,  in  wliich  the 
single  individuals  of  a  species  differed  from  one  another, 
were  changeable  and  did  change  from  one  generation  to  the 
next.  On  this  assumption  their  intricate  nature  could  hardly 
be  of  any  significance  for  the  systematist,  and  was  therefore 
almost  always  neglected. 

The  discovery  of  the  numerous  elementary  species,  of 
which  the  common  varieties  consist,  has  at  once  changed 
the  whole  aspect  of  tliis  cjucstion.  Numerous  apparently 
insignificant  marks  proved  constant  in  pure  sowings.  They 
offered  an  easy  and  rehable  means  of  distinguishing  strains 
of  widely  divergent  practical  value.  Thence  the  conclusion 
that  they  must  be  subjected  to  an  exact  study,  which  would 
enable  the  breeder  to  discover  any  new  and  useful  type  that 
might  occur  in  his  fields. 

In  order  to  do  this,  a  thorough  study  had  to  be  carried 
on  for  a  number  of  years.  The  single  characters  had  to  be 
classified,  so  as  to  give  distinct  systems.  In  these,  each 
botanical  mark  may  be  indicated  in  combination  with  its 
correlative  significance.  By  this  means,  whenever  a  cHstinct 
practical  quaUty  is  wanted,  the  correlated  botanical  marks 
may  be  looked  up  in  the  system. 

Such  elaborate  systematic  surveys  have  been  pubhshed 
from  time  to  time  by  the  experimenters  of  the  staff  of  Svalof. 


Fig.  83.     A  panicle  of  oats  -n-ith  stiff  branches,  photographed  at  Svalof, 

Sweden. 

275 


276  PLANT-BREEDING 

They  include  the  cereals,  the  peas,  some  leguminous  forage 
crops,  and  a  small  number  of  other  agricultural  plants.  As 
an  instance,  I  choose  the  system  of  the  wheat.  It  embraces 
seven  divisions,  which  are  indicated  by  the  name  of  types. 
They  are  distinguished  by  the  (jualities  of  the  ear  which  may 
be  long  or  short,  tight  or  brittle,  and  densely  or  loosely  cov- 
ered by  the  spikelets.  In  the  first  place  comes  the  vddely 
known  type  of  the  Squarehead  with  its  butt-ended  ears. 
From  tliis  are  derived  varieties  with  ovate  ears,  whose  broad- 
est part  is  seen  in  the  middle.  Cylindrical  ears  are  of  the 
same  breadth  throughout  their  whole  length,  but  in  one  type 
they  are  almost  square  and  in  another  more  or  less  flattened. 

These  types  arc  further  subdivided,  according  to  other 
marks,  each  of  them  embracing  some  four  or  five  groups 
of  minor  value.  They  are  distinguished  by  the  color,  size 
and  form  of  the  grains,  the  marks  of  the  scales,  the  occur- 
rence or  absence  of  awns  and  other  similar  marks.  All 
these  seemingly  insignificant  characters  have  been  shown  to 
be  constant  in  the  pedigree  cultures,  and  an  exact  study 
of  them  enables  the  breeder  to  recognize  each  single  type. 
So  it  is  also  with  the  minor  marks,  by  which  the  single  kinds 
arc  finally  distinguished.  Often  these  are  almost  invisible 
to  the  inexperienced  eye,  and  years  of  persevering  study  are 
necessary  to  obtain  the  faculty  of  recognizing  them  easily 
and  rapidly. 

With  this  object  in  view  a  division  of  labor  has  been 
established,  finely  adjusted  instruments  for  measurem^ents 
and  comparison  ha\e  been  invented,  and  large  collections 
of  samples  and  pictures  have  been  brought  together.  Each 
of  these  points  now  demands  our  special  attention. 

Division  of  labor  has  been  the  first  requirement,  the  study 
being  so  extensive  that  it  w^as  impossible  to  take  more  than 
one  agricultural  species  into  consideration  at  a  time. 
The   panicle  of  the  oats,  which  was  described  in  our  last 


THE   ASSOCIATION   OF   CHARACTERS  277 

chapter,  afforded  the  most  promising  instance,  and  was 
studied  first.  Soon  afterward  other  cereals  and  peas  were 
treated  in  the  same  manner,  then  vetches,  but  most  of  the 
other  agricultural  crops  have  been  taken  into  consideration 
only  during  the  most  recent  years,  or  are  still  awaiting  at- 
tention. Gradually  many  hundreds  of  dciinite  forms  were 
distinguished  witliin  each  species,  and  the  amount  of  work 
became  so  large  that  it  was  necessary  to  divide  the  subject 
among  several  investigators.  Neither  the  time  nor  the 
memory  of  one  man  was  sufficient  to  embrace  the  whole 
realm  of  the  botanical  marks  and  of  their  correlations  to 
breeding  qualities  for  all  the  elementary  forms  of  more 
than  one  or  two  species.  And  perhaps  just  this  statement 
is  the  best  way  in  which  to  convey  to  the  layman  an  idea  of 
the  enormous  amount  of  work  that  is  involved  in  tliis  study, 
and  required  for  the  complete  exploration  of  all  the  single 
forms,  now  growing  mingled  together  in  the  fields. 

At  Svalof  the  director  Dr.  Nilsson  has  chosen  for  his 
own  department,  the  cereals  and  especially  the  oats,  and  is 
assisted  in  this  work  by  Mr.  Nilsson-Ehle.  The  leguminous 
crops,  such  as  peas  and  vetches,  are  the  department  of  Dr. 
Tedin.  Rye  has  been  studied  by  Mr.  Wallden  and  potatoes 
by  jNIr.  Lundberg.  Other  special  crops  have  been  given 
into  the  hands  of  ]\Ir.  Elofson  and  ^Ir.  Witt.  Each  of 
them  has  become  a  specialist  in  his  line  and  has  acquired 
a  high  degree  of  abihty  in  singhng  out  the  rare  promising 
individuals  from  among  the  thousands  of  orchnary  specimens, 
wliich  commonly  constitute  the  majority  of  the  ordinary 
varieties.  An  instance  of  this  work  was  described  in  our 
last  chapter,  in  the  production  of  a  brewer's  barley  with 
stiff  culms.  By  such  means  it  becomes  possible  to  estimate 
the  probable  agricultural  value  of  all  aberrant  individuals. 
Whenever  a  distinct  quahty  is  desired,  either  in  order  to 
improve  a  local  variety,  or  to  bring  it  into  a  form  suited  for 


2  7<S 


PLANT-BREEDING 


other  conditions  of  soil  or  climate,  or  to  comply  with  any 
other  wishes  of  agricultural  practice,  it  is  necessary  only 
to  know  the  botanical  marks  correlated  with  the  desired 
qualities.  On  this  basis  individual  plants  may  be  singled 
out,  and  after  multiplication  through  a  few  years,  their 
progeny  will  probably  respond  to  the  demands  made,  as 
soon  as  the  industrial  qualities  themselves  are  investigated. 


Fig.  84.  A.  Spikelet  of  oat-grass  {Avemi  elatior),  showing  a  flower  with 
two  palets,  three  stamens,  and  two  stigmas  (a),  a  flower  bud  (1)),  dI' 
which  only  the  palets  are  visible  and  the  third  or  sterile  flower  (<.■'). 


Some  instances  of  correlations  may  now  be  presented. 
Different  elementary  species  of  oats  are  distinguished  by  the 
form  of  their  panicles.  Some  are  stiff  with  a  firm  principal 
axis  and  erect  branches.  In  others  the  axis  is  weak  and  the 
branches  droop.  In  some  varieties  they  are  widely  spread, 
but  in  others  they  all  bend  to  one  side.  According  to  these 
marks  definite  types  have  been  distinguished,  and  in  com- 


THE   ASSOCIATION   OF   CHARACTERS 


279 


paring  these  with  the  industrial  vahic  of  the  varieties  it  has 
been  discovered  that  stiff  and  erect  main  branches  building 
a  dense  tip  on  the  panicle  are  indicative  of  the  richest  har- 
vest and  of  the  best  kind  of  kernels.  Varieties  with  loose 
flexuous    branches    are    usually    only    poor    yiclders.     The 


==J^ 


Fig.  85.  Barley.  A.  A  complete  spikelet  with  the  three  flowers.  B 
and  C.  Single  flowers  seen  from  different  sides,  showing  two  palets,  three 
stamens,  and  the  ovary  with  the  stigmas.  In  B  also  the  two  outer  scales 
or  glumae  with  the  stigmas.     D.   Stamens  and  ovary  of  a  flower. 


number  of  the  grains  in  the  single  spikelets  affords  another 
instance.  It  is  correlated  by  distinct  laws  to  the  size  of  the 
kernels,  and  through  this  mark  to  the  industrial  value  of  the 
variety.  ^Moreover  these  numbers  arc  strictly  hereditary  and 
so  give  very  reliable  marks.     Oats  and  wheat    especially 


28o  PLANT-BREEDING 

have  been  studied  from  this  point  of  view.  In  barley,  one  of 
the  main  characters  and  one  wliich  has  been  already  alluded 
to  is  found  in  the  hairiness  of  the  scales,  bristles,  and  other 
parts  of  the  spikelets  and  flowers.  In  some  cases  the  hairs 
are  smooth  and  pressed  against  the  scales,  in  others  they 
are  stiff  and  spreading.  Crisp  and  woolly  hairs  are,  as  a 
rule,  to  be  considered  as  indicating  the  most  valuable  types. 
Experience  has  taught  that  in  this  simple  way  it  is  possible 
to  select  in  each  variety  the  elementary  form  that  will  prob- 
ably be  the  best  yielder.  The  midveins  of  the  outer  scales 
afford  still  further  marks.  In  some  cases  they  arc  smooth, 
in  others  armed  with  small  l3ut  sharp  teeth.  Even  these 
differences  are  constant  in  pure  cultures,  and  indicative  of 
correlated  yielding  quahties. 

The  same  laws  of  correlation  have  been  observed  with 
other  agricultural  plants.  Prominent  amongst  all  are  the 
forage  crops  of  the  large  family  of  the  leguminous  plants. 
Here  the  differences  between  the  numerous  elementary 
forms  witliin  the  botanical  species  are  not  so  very  small 
and  so  difficult  to  reahze  as  in  the  cereals.  Peas  and  vetches 
have  been  studied  in  the  first  place,  but  clovers,  wild  species 
of  sweet-peas,  and  several  other  forms,  whose  culture  had  as 
yet  hardly  been  profitable,  have  also  afforded  notable  results. 
For  peas  the  correlations  have  been  studied  by  Mr.  Tedin, 
who  has  pubhshed  his  results  in  tables,  giving  the  average 
weight  of  the  seeds,  their  number  in  the  pods,  and  their 
total  number  on  the  individual  plants,  in  combination  with 
other  valuable  quahties.  On  the  ground  of  this  system  he 
has  been  able  to  distinguish  500  different  kinds  of  peas, 
which  have  proven  constant  in  his  pedigree  cultures,  and 
among  which  some  40  could  be  selected  as  evidently  ex- 
celhng  the  ordinary'  varieties  out  of  which  they  had  been 
isolated. 

In  the  same  way  some  75  new  and  constant  types  of 


Fig.  86.     Svalof  Solo  pea,  a  new  forage-plant,  most  pro- 
ductive of  seeds  and  foliage.   Leaves  green. 


282  PLANT-BREEDING 

vetches  have  been  isolated  at  Svalof.  In  some  of  them  the 
flowers  are  white,  in  others  pink,  instead  of  being  purphsh, 
as  in  the  ordinary  sorts.  The  seeds  may  be  spotted  or  not, 
of  a  dark  or  of  a  pale  hue.  The  spots  are  small,  isolated,  and 
rounded  in  some  varieties,  but  in  others  they  radiate  from 
the  hilum  like  tongues  of  flame.  INIinor  marks  arc  afforded 
by  the  size  and  shape  of  the  leaves,  the  length  and  mode  of 
branching  of  the  stems,  the  distribution  of  the  pods  along 
the  branches,  and  so  forth.  All  these  marks  arc  constant, 
as  soon  as  cultures  arc  made,  each  starting  from  a  single 
parent  plant.  An  elaborate  system  of  the  vetches  has  been 
derived  from  them,  and  the  single  types  are  now  being  cul- 
tivated separately,  in  order  to  examine  their  industrial 
value. 

Similar  investigations  have  been  made  for  clover.  The 
Spanish  or  red  clover  was  formerly  imported  into  Sweden 
where  the  flrst  work  has  been  the  controlling  of  the  value 
of  introduced  sorts  and  of  their  fitness  for  the  Swedish 
cH mates.  American  sorts  of  clover  proved  too  susceptible  to 
the  hardships  of  the  Swedish  winters,  1)ut  many  of  the  kinds 
of  Middle  Europe  were  resistant  enough  to  be  cultivated  with 
success.  The  red  clover  is  very  variable,  in  respect  to  the 
shape,  and  size,  and  color-designs  of  its  leaves,  as  well  as  to 
the  flowers  and  flowerheads  and  especially  in  the  colors 
and  quahties  of  the  seeds.  A  great  number  of  types  could 
easily  be  isolated.  This  richness  in  forms  and  the  constancy 
of  the  isolated  types  had  already  been  studied  in  several 
other  countries,  as,  for  instance,  by  Schribaux  in  Paris,  and 
by  Martinet  in  Geneva,  and  their  different  commercial  value 
had  clearly  been  pointed  out.  But  by  means  of  the  method- 
ical study  of  the  botanical  characters,  which  is  the  principle 
of  the  work  at  Svalof,  a  far  larger  number  of  types  could 
be  isolated  and  varieties  be  originated  which  complied  with 
all  the  divergent  demands  of  the  soils  and  cUmates  through- 


1 

s}--                 *■■■              \ 

V 

^i1   P  IIM  1^ 

"  "-f  ^ 

--■iH'v  ' 

1 

Fig.  87.     Svalof  Grop  pea,  a  new  early  ripening  forage- 
plant. 

283 


284  PLANT-BREEDING 

out  Sweden.  Similar  results  have  been  obtained  with  the 
white  and  the  crimson  clover. 

Many  other  species  of  leguminous  plants  are  available 
for  the  culture  of  green  fodder.  Different  kinds  of  lucerne, 
of  which  the  alfalfa  is  the  best  known  species,  some  forms 
of  Lathyrus,  and  others  have  been  included  in  the  tests. 
They  are  rich  in  elementary  types,  but  even  of  the  botanical 
species  the  agricultural  signilicance  was  hardly  known. 
Some  instances  may  here  be  given.  Lathyrus  heterophyllus 
is  an  early  ripening  species,  with  sweet  tissues  and  a  vig- 
orous growth.  It  is  an  excellent  yieldcr.  Lathyrus  praten- 
sis  and  Vicia  Cracca,  two  common  species  along  road  sides 
in  Europe,  recommend  themselves  by  their  fitness  for  mixed 
cultures  on  meadows.  A  richer  type  of  Lotus  uliginosus 
with  broader  leaves  and  a  resistant  variety  of  Lathyrus 
sylvestris  have  been  isolated. 

Potatoes,  beets,  and  even  the  ordinary  meadow-grasses 
have  been  subjected  at  Svalof  to  the  same  methodical  study. 
It  would  take  too  long  to  give  all  the  details.  It  may  suffice 
to  choose  the  grasses  as  a  last  instance.  On  meadows,  the 
vegetation  is  a  more  or  less  mixed  and  motley  array  of  nu- 
merous types,  belonging  partly  to  the  grasses  and  the  legu- 
minous family,  partly  to  other  less  valuable  or  even  obnoxious 
species.  The  value  of  the  different  kinds  of  grasses  depends 
mainly  upon  the  question  whether  they  are  at  their  fullest 
development  at  the  time  when  the  hay  is  cut.  Some  species 
are  too  early,  become  woody,  and  lose  their  nutrient  quaHties 
before  the  harvest.  Others  are  too  late,  and  ha^•e  only  pro- 
duced part  of  their  foUage  at  that  time.  Both,  of  course, 
constitute  a  distinct  loss,  and  it  must  be  considered  a  chief 
aim  in  the  improvement  of  meadows  to  replace  them  by 
types  wliich  will  ripen  simultaneously. 

Now  the  experiments  at  Svalof,  although  as  yet  only 
few  in  number,  have  shown  that  the  ordinary  grasses  are 


Fig.  88.     The  wild  oat-grass  {Avena  elatior),  a 
pasture  grass. 

285 


286  PLANT-BREEDING 

at  least  as  rich  in  elementary  species  as  the  cereals.  These 
minor  types  can  be  distinguished  by  botanical  marks  which 
are  correlated  to  the  time  of  ripening  and  to  their  yielding 
qualities.  Especially  variable  are  the  common  Avena  ela- 
tior  and  the  different  species  of  Agrostis.  The  first  of  them 
gave  14  distinct  forms  in  the  first  trial,  and  later  tliis  number 
was  increased  to  about  50. 

In  concluding  this  hasty  survey  of  the  results  of  the 
methodical  study  of  correlations  at  Svalof,  I  might  emphasize 
the  great  ])rinciple  of  the  combination  of  the  scientific  and 
the  practical  sides  of  the  question.  Selection  on  the  ground 
of  practically  valuable  (|ualities  only,  has  been  the  rule  until 
very  recently.  (Jf  course  it  was  a  good  and  reliable  method, 
but  it  was  extremely  limited  in  its  application;  on  the  other 
hand,  the  whole  history  of  the  breeding  process  in  Germany 
consists  of  isolated  cases.  No  doubt  these  have  yielded 
very  valuable  results,  but  the  Svalof  principle  surmounts 
the  incumbrances  against  a  more  universal  use.  By  it  the 
breeder  is  enaljled  to  single  out  hundreds  of  valuable  strains, 
and  to  select  among  them  the  very  best.  The  search  in  the 
field  is  made  on  the  basis  of  marks  which  can  be  recognized 
instantly  by  ihc  cxijcrienced  eye,  upon  a  simple  inspection  of 
the  ears  and  ])anicles,  of  the  stems  and  their  branching,  and 
of  the  shape  and  size  of  the  leaves.  Thus  the  purely  mor- 
phological distinctions  take  the  place  of  the  agricultural 
tests,  which  embrace  measurements  and  estimates,  that  can 
hardl}'  be  made  for  single  individuals  and  never  can  be  ap- 
plied to  so  large  numbers  of  specimens  as  can  be  compared 
by  purely  scientific  marks.  A  broad  scientific  foundation  is 
thus  seen  to  be  the  means  of  abridging  the  practical  work 
and  this  to  such  a  degree  that  the  selection  may  be  extended 
and  apphed  to  almost  all  the  requirements  of  practice  at 
large. 

Two  essential  features  of  the  selection  work  at   Svalof 


THE   ASSOCIATION   OF   CHARACTERS  287 

are  still  to  be  dealt  with.  A  short  description  must  be  given 
of  some  of  the  new  instruments  for  measurement  and  com- 
parison, and  the  collections  of  samples  and  pictures  of  select- 
ed plants  must  be  mentioned.  In  the  list  of  apparatus  the 
"classificators"  may  be  described  in  the  first  place.  Tliis 
name  is  given  to  small  collections  of  say  15  to  40  ears  arranged 
according  to  a  dellnite  character.  For  each  cjuahty  a  special 
ciassificator  is  at  hand,  so  for  instance,  for  the  size,  the  shape 
and  the  density  of  the  ears.  In  order  to  classify  an  ear 
it  is  shoved  along  the  row,  until  it  falls  between  two  ears 
of  the  classilicator,  one  beyond  and  the  other  behind  it. 
The  intervals  between  every  two  succeeding  ears  of  the 
apparatus  being  marked  by  figures,  the  figure  on  wliich 
the  ear  falls  is  the  indicator  of  its  degree  of  the  character  in 
question. 

The  transparency  of  the  grains  of  barley  is  measured 
by  means  of  screens  with  holes.  These  are  exactly  filled 
by  one  grain  each,  and  the  standard-kernels  are  arranged 
according  to  the  degree  of  their  diaphaneity.  The  grains 
to  be  tested  are  put  into  similar  holes  of  a  httle  separate 
screen,  which  can  be  shoved  along  the  ciassificator  until 
their  transparency  coincides  with  that  of  one  of  the  standard 
types.  The  degree  of  mealiness  is  tested  by  a  small  pincer 
which  measures  the  pressure  required  to  squeeze  the  ker- 
nels into  pieces.  Other  instruments  are  so  constructed  that 
they  collect  from  an  ear  or  a  panicle  all  the  lowest  grains, 
all  those  of  the  second  rank  and  so  on,  in  order  to  determine 
the  average  weight  of  each  group  separately.  As  we  have 
seen,  the  seat  of  the  heaviest  kernels  is  one  of  the  important 
marks  in  the  testing  of  \-arieties  of  cereals.  Many  other 
instruments  have  been  devised  in  order  to  make  the  esti- 
mates as  independent  of  personal  impressions  as  possible, 
and  thus  to  make  them  thoroughly  reliable  even  if  they 
have  been  made  in  different  years  or  in  different  locahties. 


288  PLANT-BREEDING 

From  these  short  descriptions  it  is  easily  seen  that  one 
of  the  aims  of  the  method  of  selection  is  the  gracUng  of  all 
marks  in  figures.  By  this  means  it  becomes  possible  to 
give  extensive  comparative  surveys  of  whole  groups  of  newly 
selected  plants  or  of  the  strains  derived  from  them  and  to 
draw  a  parallel  between  the  new  and  the  already  existing 
varieties.  "Without  it  the  testing  of  the  value  of  many 
hundreds  of  new  types  would  evidently  be  scarcely  possible. 

With  the  same  object  in  view  larger  collections  have 
been  made  and  separate  buildings  have  been  erected  in 
order  to  exhibit  them  in  such  a  way  that  they  are  easily 
accessible  whenever  a  new  form  must  be  compared  with  the 
older  types.  For  the  testing  is  by  no  means  Hmited  to  the 
ears  and  the  kernels,  but  embraces  the  whole  plant,  during 
the  several  periods  of  its  development.  Dried  spec- 
imens of  seedhngs  must  be  at  hand  for  all  of  the  useful  varie- 
ties. The  manner  in  which  the  culms  produce  their  more 
or  less  numerous  side  halms  must  be  illustrated,  also  the 
length  and  the  stiffness  of  the  straw,  on  which  nearly  the 
whole  value  of  some  varieties  depends.  ^Moreover  the  varie- 
ties are  not  only  to  be  compared  with  one  another,  but  their 
constancy  must  be  tested,  and  for  this  purpose  some  spec- 
imens of  previous  years  must  be  preserved.  In  this  way 
pedigrees  of  dry  specimens  have  been  built  up,  which  convey 
to  the  visitor  an  idea  of  the  whole  previous  history  of  the 
race,  and  contain,  besides  the  proofs  of  its  constancy,  the 
indications  of  any  deviation,  which  may  have  occurred  in  it. 

These  collections  are  to  be  considered  as  living  expres- 
sions of  the  systems  described  before.  The  investigator 
\dsits  them  with  the  plant  he  wishes  to  classify,  and  is  guided 
by  their  arrangement  so  that  he  may  find  the  corresponding 
prototype  in  the  easiest  way.  They  have  this  great  advantage 
over  the  printed  systems  that  all  the  single  quahties  may 
be    taken    into    consideration    at  once,   without   the  labo- 


THE  ASSOCIATION   OF   CHARACTERS  289 

rious  comparison  of  the  figures  in  the  tables.  It  is  almost 
superfluous  to  mention  that  the  collections  are  largely 
illustrated  by  drawings  and  photographs,  and  that  charts 
giving  the  results  of  the  tables  in  a  statistical  way  facilitate 
the  work.  Pedigrees  have  been  drawn  for  most  of  the 
important  novelties  of  the  station. 

The  work  of  Dr.  Nilsson  and  his  staff  at  the  Swedish 
agricultural  experiment  station  at  Svalof  is  a  model  of  the 
combination  of  science  and  practice.  The  problems  it  has 
to  solve  are  purely  practical  ones,  but  the  method  depends 
upon  exact  scientific  studies.  The  station  is  a  private 
enterprise,  founded  by  the  Swedish  agriculturists  for  their 
own  direct  use;  it  has  neither  to  serve  educational  aims, 
nor  to  yield  results  of  theoretical  significance.  No  purely 
scientific  researches  are  carried  on,  no  grouping  of  results 
with  the  sole  object  of  contributing  toward  the  solution  of 
biological  problems  is  allowed.  But  its  experience  has 
taught  the  indispensableness  of  scientific  principles  and 
methods.  Only  under  their  guidance  may  the  practical 
work  be  kept  witliin  limits  which  guard  it  against  useless 
and  superfluous  experiments,  and  which  cause  it  to  attain 
its  purpose  by  the  shortest  and  most  direct  way.  This 
method  of  applying  science  to  practice  has  opened  previously 
unsuspected  possibiUties  and  discovered  new  fields  of  in- 
vestigation in  the  study  of  the  highly  interesting  relations 
between  botanical  marks  and  quahties  of  practical  value. 
It  will  soon  bear  fruit  for  the  doctrine  of  evolution  and  for 
the  theory  of  specific  units  in  addition  to  its  conspicuous 
results  for  agricultural  practice. 

D.      CORRELATIONS    IN    FLUCTUATING   VARIABILITY 

Correlation  is  the  name  given  to  regular  coincidences  of 
apparently  independent  characters  and  marks.  This  reg- 
ularity is  not  meant  to  be  absolute;  it  simply  means  the  more 


290  PLANT-BREEDING 

or  less  frequent  occurrence  of  the  observed  combinations. 
On  the  other  hand  the  conception  does  not  exclude  cases  of 
complete  mutual  dependency  of  characters;  it  is  even  prob- 
able that  it  embraces  many  of  them,  but  that  our  knowledge 
is  still  too  incomplete  to  allow  us  to  draw  a  distinction  be- 
tween these  and  the  ordinary  cases.  The  other  extreme  in 
the  long  list  of  possible  combinations  is  evidently  given  by 
casual  and  fortuitous  coincidences,  accidentally  repeated 
in  some  group  of  observations.  A  continued  investigation 
would  show  these  to  have  no  real  value,  and  so  they  may 
here  be  left  out  of  consideration. 

After  our  hasty  survey  of  some  of  the  most  interesting 
facts,  we  may  now  proceed  to  inquire  into  their  causes. 
These  may  be  brought  under  two  heads.  The  causes  may 
be  internal  or  external.  In  other  words  the  correlation  may 
depend  on  some  inner  connection  of  the  qualities,  or  simply 
on  corresponding  changes  induced  by  environmental  in- 
fluences. Evidentl}',  the  internal  correlations  are  the  most 
interesting,  and  moreover  those  which  may  be  the  most 
completely  reHed  upon.  Outer  life-conditions,  working  in 
the  same  direction  on  different  characters,  on  the  other  hand, 
are  more  easily  understood  and  more  directly  accessible  for 
experimental  study.  On  this  account  a  rational  treatment 
will  have  to  begin  with  the  latter,  and  discuss  the  former 
or  internal  causes  of  correlation  only  after  the  field  has  been 
cleared  as  much  as  possible  of  its  foreign  elements. 

For  this  reason  I  have  chosen  for  this  chapter  the  study 
of  the  influence  of  external  life-conditions  on  the  phenomena 
of  correlation. 

Correlated  variabihty  is  (|uite  an  ordinary  feature  in  all 
plant  life.  It  may  be  seen  almost  e\'erywhere.  As  soon  as 
■a  plant  deviates  from  its  type,  it  will  be  disposed  to  do  so  in 
more  thin  one  character.  This  rule  holds  good  for  rare  and 
casual  aljnormalities,   as  well  as  for  the  more  normal,  so- 


Fig.  80      A  pitcher-like  leaf  of  tobacco. 


291 


292  PLANT-BREEDING 

called  fluctuating  deviations  from  the  type.  Useful  qualities 
are  subjected  to  it  as  well  as  those  practically  useless  marks, 
which  are  usually  studied  merely  on  account  of  the  valuable 
indications  they  so  often  give  for  comparative  science. 

Some  of  our  most  convincing  arguments  may  be  derived 
from  the  study  of  teratological  phenomena.  Every  one 
who  is  collecting  monstrosities,  knows  that  they  are,  to  a 
high  degree,  dependent  on  the  influence  of  the  enxironment. 
Some  years  are  known  to  be  rich,  and  others  poor  in  abnor- 
mal developments.  One  of  the  most  notable  instances  is 
the  year  185 1,  in  the  summer  of  which  pitcher-Hke  leaves 
appeared  in  such  large  numbers,  as  to  be  regarded  as  a  dis- 
tinct disease.  This  was  the  case  in  the  western  districts 
of  Belgium,  and  while  roses  and  other  plants  were  notably 
affected,  the  damage  done  to  the  tobacco  cultures  was  re- 
ported to  be  quite  heavy.  In  Baden  the  summer  of  1886 
and  around  Paris  the  fall  of  1893  are  described  as  exception- 
ally rich  in  abnormal  productions,  and  other  instances  could 
easily  be  given.  Evidently  some  external  cause  was  at 
work,  and  high  temperature  and  moisture  are  among  the 
factors  called  upon  by  different  authors  to  explain  the  fact 
which  so  deeplv  impressed  them. 

In  a  single  locality  the  same  phenomenon  may  often  be 
obseiA'ed.  Some  hillslopes  and  some  fields  are  productive  of 
monstrosities,  while  others  are  not.  By  this  means  a  bota- 
nist is  often  enabled  to  discover  the  localities,  which  may 
give  him  the  de^iations  he  wishes  to  collect.  Sometimes  it  is 
one  species  which  offers  a  profusion  of  interesting  instances; 
in  other  cases  a  more  or  less  large  number  of  plants  arc 
included  in  the  phenomenon.  This  observation  is  often 
stated  by  sa\ing  that  a  monstrosity  is  seldom  seen  alone; 
it  is  quite  generally  accompanied  by  others. 

Some  instances  may  be  given  as  proofs.  Pitchers  are 
ordinarily  built  out  of  one  leaf,  or  of  some  part  of  it,  but 


THE   ASSOCIATION    OF    CHARACTERS 


293 


together  with  them  two-bladed  pitchers  may  not  rarely  be 
observed,  as  in  the  magnolia  and  the  common  plantain. 
The  pelories  of  the  foxgloves  are  almost  always  the  seat  of 
secondary  deviations,  such  as  tube-like  petals,  fissions  of  the 
corolla,  multiplication  of  the  stamens,  the  production  of  a 
secondary  raceme  from  within  the  capsule,  and  so  on.     Even 


Fig.  90.  Pitchers  of  Magnolia,  A,  B,  C.  Of  clover,  D,  E.  Of  the 
lime  tree  (Tilia),  F,  G,  One-leaved  pitchers.  C.  Two-leaved.  A.  Upper 
part  of  a  leaf  only  transformed  into  a  pitcher.  D,  E.  Pitcher-like  leaflets  of 
the  ordinary  and  of  the  five-leaved  clover. 

the  beautiful  erect  pelories  of  our  cultivated  Gloxinias  often 
show  deviations  from  the  normal  number  of  tips  of  the 
corolla  and  of  stamens.  Fasciations  are  usually  combined 
with  cleft  leaves  and  other  allied  monstrosities,  and  twisted 
stems  are  so  rich  in  their  deviations  as  to  afford  sufficient 
material  for  quite  a  large  field  in  the  science  of  teratology. 


294  PLAXT-B  R I-:  I-:  I  )rN("r 

On  this  i)rinciple  of  correlation  a  defniitL-  method  of 
scarchinij;  for  monstrosities  has  been  founded.  Years  agjo 
I  was  impressed  by  the  fact  that  deviations  in  the  seedhng 
plants  are  often  followed  ])y  abnormalities  in  the  adult 
state.  By  this  means,  the  cotyledons  of  the  scedUngs  may 
give  indications  of  what  is  to  be  expected.  Now  it  is  as 
easy  to  inspect  thousands  of  germinating  plantlets  as  it  is 
difficult  to  cultivate  the  same  numljer  to  their  full  develop- 
ment. But  by  choosing  the  stray  seedhngs  with  three 
seed-leaves  or  with  connate  cotyledons,  the  cultures  may  be 
effectively  reduced,  the  chance  of  producing  monstrosities 
on  a  given  space  being  proportionately  increased. 

Leaving  the  abnormal  characters,  we  have  now  to  con- 
sider a  group  of  observed  cases  of  correlations  in  ordinary 
deviations.  I  choose  mv  instances  from  among  the  am- 
cultural  plants.  Fruwirth  has  studied  the  relations  in 
the  development  of  leguminous  crops,  at  the  agricultural 
station  of  Hohenheim  in  Wiirtemberg.  He  observed  a 
parallelism  between  the  increase  of  the  total  harvest  and  the 
weight  of  the  pods,  the  number  and  the  weight  of  the  seeds. 
Less  intimately,  but  still  clearly  correlated  with  these  char- 
acters was  the  average  size  of  the  seeds  and  the  average 
height  of  the  whole  plants.  Gwallig  observed  that  large 
kernels  are  as  a  rule  richer  in  albuminous  substances 
than  small  ones.  Tliis  relation  has  been  found  to  hold 
good  especially  for  peas  and  lupines,  both  belonging  to  the 
same  family  and  often  cultivated  as  forage  crops. 

Flax  has  been  studied  in  tliis  respect  by  Schindler,  who 
stated  that  the  length  of  the  fibers  and  their  total  amount 
are  correlated  with  the  total  height  of  the  plant,  measured 
from  the  root  to  the  liighcst  capsule.  The  thickness  of  the 
stem  is  inversely  correlated  with  its  height,  higher  plants 
having  thinner  stems.  Therefore,  for  the  harvest  of  the 
fibers  the  thinner  specimens  and  strains  should  be  preferred. 


Fig.  91.  A.  Seedling-plants  of  Evening-primroses.  B.  Of  the  figwort 
{Scrophiilaria  nodosa).  C.  Of  Silene  odontipetala.  D.  Of  poppies.  E. 
Of  the  beech.  A  i  and  D  i  normal  seedlings.  A  7,  B,  C  2,  D  4,  E,  . 
Tricotyledonous  seedlings.  C  3,  D  5,  Seedlings  with  four  and  D  6  with 
five  seed-leaves.  A  2-6,  C  i,  D  2-3.  Different  degrees  of  splitting  of 
seed-leaves. 


295 


296  PLANT-BREEDING 

Tall  plants  are  less  branched  than  smaller  ones,  and  bear 
a  correspondingly  smaller  number  of  capsules  and  of  seeds. 
Potatoes  have  often  been  an  object  for  comparative  measure- 
ments of  their  different  parts  and  a  survey  of  their  correlations 
shows  that  these  are  cjuite  numerous.  It  may  sufiice  to 
merely  point  out  the  parallelism  between  the  average  number 
and  weight  of  the  tubers  on  a  plant,  the  number  of  stems, 
and  the  amount  of  starch  in  the  potatoes. 

Many  other  instances  could  be  given.  They  all  give 
proof  of  a  high  degree  of  paralleHsm  between  the  different 
organs  of  a  plant,  increasing  development  of  one  cjuahty 
being  combined  with  increase  or  decrease  of  other  points 
according  to  definite  rules.  By  this  means  selection  may 
be  guided,  as  we  have  seen  in  a  previous  chapter.  But  the 
cultural  treatment  may  be  furthered  also  by  the  observation 
of  such  correlations,  because  in  stimulating  the  develop- 
ment of  some  parts  we  may  expect  to  increase  the  size  or 
wei<rht  of  others  at  the  same  time.  An  exact  knowledge 
of  these  phenomena  is  thus  of  paramount  interest  for  agri- 
cultural practice,  and  the  difficult  and  tedious  study  of  all 
its  features  should  be  diligently  carried  through  until  definite 
principles  for  the  practical  work  may  be  derived  from  it. 

Inquiring  into  the  causes  of  the  parallelism  of  apparently 
independent  characters,  we  have  first  to  state  that  it  is  often 
difficult  to  decide  whether  the  observed  combinations  are 
due  to  internal  or  to  external  causes.  Among  the  facts 
I  have  cjuoted,  there  can  be  no  doubt  that  at  least  a  large 
majority  are  due  to  external  influences.  On  the  other  hand, 
more  intimate  or  internal  relations  may  be  hidden  in  some 
instances  without  our  being  able  to  discern  them  and  thus 
to  classify  our  group  of  phenomena.  Our  only  way  is  to 
leave  them  out  of  consideration  until  further  investigation 
will  have  pointed  them  out  and  to  consider  our  facts  as 
uniform  and  as  the  result  of  the  same  causes. 


THE   ASSOCIATION   OF   CHARACTERS  297 

External  influences  can  affect  a  plant  only  because  of 
some  kind  of  responsiveness  which  must  be  present  in  it. 
Without  such  no  reaction  will  be  produced.  This  assertion 
may  seem  to  be  a  truism,  but  even  as  such  it  m.ay  help  us 
to  reach  a  better  view  of  the  relation  under  discussion. 
For  it  is  clear  that  a  parallel  action  of  the  external  factors 
demands  a  corresponding  response  of  the  characters  to  them, 
and  we  may  base  our  discussion  upon  this  assumption, 
making  the  state  of  sensibiHty  its  chief  aim. 

As  a  rule,  all  variable  parts  are  influenced  by  the  same 
factors.  Among  them  the  nutritive  are  most  prominent. 
Other  agents,  such  as  temperature,  moisture,  and  Hght, 
cooperate  with  these  in  a  more  or  less  considerable  degree. 
Many  authors,  however,  take  their  significance  to  be  only 
secondary,  inasmuch  as  the  nourishment  itself  may  be 
changed  by  them.  On  the  basis  of  this  conception,  nutrition 
would  be  the  main  factor  in  all  fluctuating  variabiHty. 

Now  it  is  evident,  that  all  development  depends  in  the 
first  place  upon  the  amount  of  available  food.  This  simple 
sentence  gives  a  key  to  at  least  a  large  group  of  the  phe- 
nomena of  correlation.  \Mienever  the  size  of  the  seeds 
increases  wdth  the  weight  of  the  whole  harvest,  or  the  number 
of  seeds  in  a  pod  with  the  height  and  degree  of  branching  of 
the  plant,  there  can  be  no  doubt  that  all  these  qualities 
depend  upon  the  nourishment,  and  that  it  is  tliis  factor 
which  causes  them  all  to  increase  or  to  decrease  at  the  same 
time. 

This  rule  will  be  more  easily  understood  if  w^e  take  a 
definite  example.  As  such  I  choose  a  variety  of  cultivated 
poppies,  belonging  to  the  ordinary  tall  species  or  opium- 
poppy  (Papaver  somniferum).  Numerous  forms  of  this 
beautiful  plant  are  cultivated  in  our  gardens.  The  most 
pecuHar  among  them  is  the  variety  in  which  the  stamens 
are  partly  converted  into  pistils.     These  secondary  pistils 


298  PLANT-BREEDING 

surround  the  capsule  by  a  lar<:;e  crown  of  slender  and  green 
organs,  which  persist  after  the  i)etals  and  stamens  are 
fallen  off,  and  thus  heighten  the  ornamental  effect  of  the 
fruits.  Only  the  innermost  rows  of  stamens  arc  changed 
in  this  way.  Both  the  iilament  and  the  anther  are  affected, 
the  former  being  dilated  into  a  sheath,  in  whose  cavity  the 
ovules  arc  produced.  Ordinarily  these  latter  are  only 
imperfectly  developed  and  the  bright  crown  of  secondary 
pistils  contril)ute  little  if  any  to  the  fertility  of  the  ilower. 

What  makes  this  variety  especially  suitable  for  our  dis- 
cussion is  the  liigh  degree  of  variability  in  the  development 
of  this  crown  of  pistillodous  stamens.  In  some  instances 
it  is  seen  to  be  so  broad  as  to  have  affected  a  large  majority 
of  the  stamens;  in  others  only  one  or  two  of  these  parts  are 
changed,  and  in  extreme  cases  only  a  single  hardened  and 
persisting  filament  without  an  ovarial  ca\ity  and  without 
stigma  indicates  the  type.  All  intermediate  forms  may  be 
found  and  the  variabiHty  covers  a  range,  going  from  one 
pistil  up  to  a  hundred  and  fifty  and  sometimes  even  more. 
Unfortunately  these  altered  organs  often  show  another 
anomaly,  consisting  in  a  coalescence  of  some  of  them,  thereby 
constituting  groups,  in  which  it  is  difllcult  to  distinguish  and 
count  the  single  parts.  In  extreme  cases  this  coalescence 
may  be  such  as  to  combine  all  the  changed  stamens  into  a 
narrow  cup  around  the  normal  capsule,  and  more  com- 
monly a  more  or  less  divided  ring  of  such  groups  is  observed. 
It  is  easily  seen  that  the  variabiHty  of  this  character  affords 
an  excellent  material  for  the  study  of  its  dependency  on 
outer  influences.  We  may  make  sowings  under  different 
circumstances,  giving  them  a  sunny  or  a  shaded  place,  good 
or  bad  soil,  different  quahties  of  manure,  watering  or  keep- 
ing them  dry,  protecting  the  young  plants  under  glass  or 
exposing  them  to  all  the  effects  of  the  weather,  and  so  on. 
If  we   do   so   we   easilv   find   that   all   favorable   conditions 


Fig.  92.  Polyccphalous  opium  poppy.  A.  Xormal  fruit.  B.  The  same 
cut  longitudinally.  C,  D.  Normal  stamens.  E,  F.  Stamens  transformed 
into  secondary  carpels.  G,  H,  I.  Secondary  carpels,  cut  transversely  with 
one.  two,  and   four  rows  of  seeds. 


?90 


300  PLANT-BREEDING 

increase  the  crown  of  pistillodous  stamens,  while  adverse 
influences  reduce  the  change  and  thus  favor  the  production 
of  the  normal  organs. 

The  same  influences,  however,  govern  the  degree  of 
development  of  the  whole  plant,  the  height  and  the  thickness 
of  the  stem,  the  size  of  the  flower  and  the  fruit,  the  number 
and  the  strength  of  the  branches,  and  even  the  extent  of  the 
foHage.  Hence  we  may  expect  a  correlation  betv^een  the 
abnormality  and  the  growth  of  all  the  normal  parts,  and  it  is 
quite  easy  to  control  tliis.  The  best  means  is  to  choose  the 
ripe  capsules.  Their  size  and  weight  is  evidently  the  result 
of  the  activity  of  the  whole  plant,  during  the  whole  time 
of  its  life,  and  thus  may  be  considered  as  a  standard  for 
comparison. 

In  a  bed  of  pistillodous  poppies,  we  pick  out  a  group 
of  fullgrown  fruits  and  arrange  them  according  to  their 
size,  taking  as  a  measure  either  the  height  or  the  weight  of 
the  central  capsule  without  the  crown  of  secondary  organs. 
Then  we  compare  the  degree  of  development  of  the  anomaly 
with  this  size,  and  we  And  an  almost  complete  parallelism. 
The  smallest  fruits  are  devoid  of  appendixes  or  nearly  so, 
and  the  largest  ones  bear  the  richest  crowns.  Between 
these  extremes  the  number  of  the  altered  stamens  regularly 
increases  with  the  size  of  the  fruit,  hardly  any  deviation 
from  the  most  complete  parallelism  occurring. 

By  this  investigation  the  normal  and  the  abnormal 
development  are  proven  to  be  as  closely  correlated  as  might 
be  expected.  So  it  is  also  in  other  instances.  Ordinarily, 
of  course,  abnormahties  are  too  rare  to  permit  of  such  a 
complete  comparison,  but  notwithstanding  this,  common 
experience  shows  them  to  be  connected  with  strong  growth 
and  favorable  life  conditions.  This  relation  is  often  so 
striking  that  in  former  times  it  was  simply  assumed  that 
monstrosities  could  be  produced  by  an  excess  of  nourishment, 


Fig.  93.  Young  plant  of  opium  poppy  in  the  sensitive  period  of  the 
development  of  the  terminal  flower,  cut  longitudinally.  A.  Flower-head  of 
June,  7.  B.  June,  14.  C.  All  parts  discernible.  D.  Diagram  of  flower. 
E.  Diagram  of    young    flowerbud.     P.  Petals.     S.  Stamens. 


301 


302  PLANT-BREEDTNG 

but  ;it  ])resent  it  is  known  that  the  faculty  of  producing  them 
must  be  present  beforehand,  and  that  the  food-supply  can 
only  stimulate  the  frequency  of  occurience  and  the  degree 
of  dew'lopment. 

We  may  now  proceed  one  step  farther  and  incjuire  into 
the  time  at  which  the  external  influences  can  affect  the  size 
and  the  form  of  the  organs.  It  is  evident  that  these  agencies 
must  be  limited  to  the  period  of  youth,  because  as  soon  as 
the  growth  ceases,  no  further  change  is  possible.  Here, 
however,  the  form  and  the  size  must  be  considered  separately, 
the  form  being  definitely  fixed  long  before  the  size  of  the 
organ  is  determined.  We  thus  come  to  this  conception 
in  regard  to  periods  of  sensibility,  tliat  the  one  for  the  form 
ceases  earHer  than  that  of  the  ultimate  increase. 

The  pistillodous  opium-poppy  may  once  more  be  chosen 
as  an  example.  If  we  examine  a  young  plant  six  or  seven 
weeks  old  we  find  a  short  stem  bearing  a  group  of  leaves 
which  surpass  it  in  size  many  times.  The  young  bud  of 
the  flower  is  attached  at  the  head  of  tlie  stem.  Its  calyx 
covers  the  innermost  parts,  which  are  still  \ery  small.  The 
central  capsule  hardly  begins  to  be  differentiated  and  the 
whorl  of  stamens  is  seen  as  a  smooth  wall  of  soft  tissue 
around  it.  At  this  period  the  normal  and  the  pistillodous 
stamens  are  still  aw^aiting  the  first  manifestation  of  their 
form.  Shortly  afterward  they  may  be  seen  as  small  protuber- 
ances, rounded  and  without  distinct  form,  but  gradually 
increasing  and  assuming  more  definite  types.  At  this  time 
there  is  still  no  visible  distinction  between  the  normal  and 
the  pistillodous  stamens,  and  it  is  not  possible  to  decide 
whether  the  bud  would  grow  into  a  rich  or  into  a  poor 
representative  of  the  variety.  A  few  days  afterwards, 
however,  the  decision  becomes  apparent,  and  the  period 
of  sensibility  closes. 

Exact  limits  for  this  period  of  sensibility  to  the  external 


Fig.  94.     The   double  corn-marigold,  an  cxjjerimentally  produced    variety. 


503 


304  PLANT-BREEDING 

life-conditions  cannot,  of  course,  be  set  from  these  observa- 
tions. But  we  do  not  need  them  for  our  present  discussion. 
The  main  fact  is  that  all  organs  and  cjuaUties  must  go  through 
such  a  responsive  period,  and  that  this  period  coincides, 
at  least  partly,  with  their  extreme  youth.  Hence  we  may 
derive  a  general  rule  for  the  correlations  depending  on 
fluctuating  variabiHty.  For  it  is  evident  that,  with  the 
continuous  change  of  the  weather,  only  such  organs  are 
really  exposed  to  the  same  life-conditions,  as  arc  sensible 
to  them  at  the  same  time.  As  soon  as  the  period  of  sensi- 
bility has  passed,  the  weather  can  no  longer  have  an  influence, 
but  new  parts  are  produced  which  will  be  exposed  to  the 
influences  prevailing  at  that  time.  In  this  way  we  may 
conclude  that  one  of  the  great  factors  of  correlation  is 
equahty  of  age,  because  it  exposes  the  organs,  during  the 
period  of  their  sensibiHty,  to  the  same  conditions. 

Another  cause  of  correlation  may  be  looked  for  in  the 
mutual  dependency  of  different  organs,  the  one  affording 
or  controlhng  the  nourishment  for  the  other.  This  case, 
however,  though  of  quite  common  occurrence,  cannot  always 
be  easily  separated  from  the  first,  botli  causes  ordinarily 
combining  their  cilorts  in  the  same  direction. 

It  may  be  stuched  by  the  statistical  method.  A  hundred 
or  more  individuals  are  measured,  and  the  result  is  represented 
by  a  single  Hne.  In  order  to  do  this,  the  individuals  are 
arranged  according  to  the  degree  of  development  of  the 
measured  quahty.  Suppose  we  compare  the  amount  of  sugar 
in  the  sugar-beets  of  a  field.  This  amount  can  be  measured 
for  a  part  of  the  tissue,  without  sacrificing  the  beet,  allowing 
thereby  the  selection  and  the  ulterior  cultivation  of  the  best 
samples.  As  is  generally  known  the  sap  is  pressed  from 
the  tissue  and  after  clearing  it,  the  percentage  of  sugar  is 
determined  by  the  method  of  polarization.  In  the  year 
1896,   I  had  an  opportunity  of  studying  these  percentage 


Fig.  95.  \'ariability  in  the  size  of  the  ripe  fruits  of  the  Evening-primrose 
of  Lamarck.  A.  A  weak  plant  with  small  fruits.  B.  A  tall  plant  with 
large  fruits. 


305 


3o6  PLANT-BREEDING 

figures  for  some  40,000  beets,  cultivated  on  the  fields  of 
Messrs.  Kuhn  &  Co.,  at  Naarden,  in  Holland,  and  examined 
in  their  laboratory  for  purposes  of  selection.  The  average 
percentage  was  15.5,  the  extremes  going  up  to  19  and  coming 
down  to  about  12  per  cent.  These  extremes,  however, 
were  comparatively  very  rare,  especially  on  the  upper  side 
of  the  group,  where  only  a  few  individuals  reached  the  very 
limit.  IMore  than  one  half  of  all  the  beets  differed  less  than 
one-half  per  cent  from  the  average,  the  total  number  of 
roots  with  15  to  16  percent  sugar  being  about  twenty-two 
thousand.  On  both  sides  of  this  central  group  the  number 
of  beets  rapidly  decreased  with  the  increasing  degree  of 
deviation  from  tiic  average  value. 

In  the  same  manner  the  fluctuating  variability  of  other 
qualities  and  other  characters  may  he  given  under  the  form 
of  a  curve.  The  ray- florets  on  the  heads  of  the  composites 
can  easily  be  counted  for  hundreds  and  even  for  thousands 
of  single  flower-heads,  and  the  figures  thus  obtained  will 
show  a  similar  grouping  around  an  average  number.  In  the 
marigolds  this  number  is  13,  in  the  daisies  21,  and  the  same 
figures  are  met  with  on  the  flower-heads  of  numerous  other 
species.  The  size  of  fruits  and  capsules  may  be  treated 
in  the  same  way.  1  measured  the  capsules  of  over  five 
hundred  individuals  of  an  evening  primrose  and  got  a  curve 
that  did  not  differ  essentially  from  that  of  the  sugar  beets 
just  mentioned.  The  average  individuals  bore  capsules  of 
nearly  2.5  cm.  and  the  extremes  reached  1.5  and  3.4  cm. 
The  largest  capsules  were  thus  seen  to  have  about  double 
the  size  of  the  smallest  ones.  Between  these  limits  the 
different  sizes  were  grouped  in  such  a  way  that  more  than 
half  of  the  individuals  could  be  said  to  have  fruits  of  medium 
size,  the  remaining  sizes  being  respectively  rarer  the  more 
they  differed  from  the  average. 

If  now  we  compare  this  size  of  the  capsules  of  the  evening 


THE  ASSOCIATION   OF   CHARACTERS  307 

primroses  with  the  remaining  qualities  of  the  plants,  we 
observe  a  definite  case  of  correlation.  Small  capsules  are  the 
product  of  weak  stems,  long  ones  are  borne  only  by  stout 
individuals.  A  curve,  made  for  the  height  of  the  plants 
would  run  nearly  parallel  to  that  of  the  capsules.  Com- 
paring weak  branches  with  the  main  spike,  we  find  the  same 
arrangements,  the  capsules  on  the  former  being  decidedly 
smaller.  I  have  made  some  cultures  with  this  species  in 
order  to  study  the  correlation  of  the  capsules  and  the  general 
degree  of  development  under  the  influence  of  different 
outer  conditions  of  life.  By  ginng  more  manure,  a  better 
exposure,  or  more  adequate  treatment,  it  is  easy  to  get  much 
stouter  stems,  with  a  richer  system  of  branches  and  increased 
foliage.  Along  with  these  marks  the  capsules  are  seen 
to  increase  in  size,  their  medium  length  coming  up  from 
2.5  to  3.5  cm.  and  their  maximum  reaching  even  4.5  cm. 

It  is  evident  that  the  growth  of  the  capsules  in  part 
runs  parallel  with  that  of  the  other  organs  of  the  plant, 
and  in  part  depends  upon  them.  A  stouter  stem,  with 
larger  and  more  numerous  leaves,  produces  more  nourish- 
ment for  the  flowers  and  fruits  and  thereby  will  make  them 
bigger.  On  the  other  hand,  the  tall  individuals  are  largely 
those  which  have  found,  from  their  very  youth,  the  most 
favorable  conditions  of  soil,  of  water,  of  exposure,  and  of 
other  influences,  and  inasmuch  as  these  factors  are  still 
at  work  during  the  responsive  period  of  the  development 
of  the  fruits,  they  will  directly  affect  them  in  the  same 
direction.  Thus  we  see  that  in  such  cases  the  causes  of 
correlation  are  twofold,  the  one  acting  directly,  the  other 
indirectly,  and  influencing  the  younger  organs  through  the 
degree  of  development  of  the  older  ones. 

Returning  to  the  sugar  beets,  we  may  give  our  attention 
to  the  correlations  which  the  two  main  points  in  their  life 
may  exhibit   with   the   more   easily   appreciated    characters 


3o8  PLANT-BREEDING 

of  the  roots  and  of  the  foliage.  One  of  these  two  main 
points,  of  course,  is  the  percentage  of  sugar  in  the  sap.  The 
other  point  is  the  quahty  of  the  seeds,  since  on  this  f[uaUty 
the  harvest  of  the  next  year  chiefly  depends.  Now  it  is 
evident  that  of  our  two  groups  of  causes  which  determine 
the  phenomena  of  correlation  of  fluctuating  variability,  only 
the  second  one  comes  into  consideration.  This  correlation 
may  be  simply  stated  l^y  saying  that,  as  a  rule,  stouter  plants 
will  be  richer  in  sugar  and  produce  better  seeds.  Nearly 
all  other  causes,  however,  which  govern  the  amount  of  sugar 
in  the  roots  of  the  first  year  will  be  without  influence  on  the 
C[uality  of  the  seeds.  Local  variations  in  soil,  in  moisture, 
and  especially  in  the  amount  of  space,  when  this  is  increased 
on  account  of  the  falling  out  of  some  neighbor,  will  directly 
influence  the  sugar  percentage,  which  may  also  be  dimin- 
ished by  insects  feeding  on  the  leaves  or  by  other  diseases. 
In  the  second  year  the  roots  will  be  planted  in  other  fields 
and  with  other  conditions  of  soil  and  exposure,  and  during 
the  time  of  production  of  seeds  the  single  individuals  will 
occupy  C|uite  different  places  on  the  curve  of  variability  than 
those  they  held  the  first  year. 

Hence  we  may  conclude  that  the  correlation  between  the 
percentage  figure  for  the  root  of  the  first  year,  and  the  real 
value  of  the  seeds  is  only  a  very  feeble  relation.  The  richest 
roots  may  yield  only  poor  seeds  and  conversely.  In  other 
words,  the  percentage  figures,  which  are  now  the  universally 
accepted  criterion  for  the  selection  of  beets  for  the  produc- 
tion of  seed,  are  only  an  imperfect  indication  of  the  equality 
of  the  latter.  Direct  experiments  have  often  shown  the 
accuracy  of  this  conclusion,  and  the  breeders  of  sugar-beets 
know  very  well  that  single  excellent  roots  may  not  be  relied 
upon  at  all  for  the  production  of  exceptionally  good  seed. 
They  rely  only  on  the  average  of  the  selected  beets,  and 
rightly  assume  that  the  larger  the  group  of  their  roots,  the 


THE   ASSOCIATION    OF    CHARACTERS  309 

better  is  the  chance  that  their  seeds  will  be  of  superior  qual- 
ity. Selection  of  seed-bearers  based  on  a  direct  measure- 
ment of  their  average  progeny,  as  it  was  originally  apphed 
by  Yilmorin,  seems  at  the  present  time  to  be  too  troublesome 
for  practice,  though  theoretically  it  would  be  much  less  open 
to  criticism,  and  though  in  the  long  run  it  would  also  yield 
better  practical  results. 

Such  arc  the  laws,  which  govern  that  most  complicated 
phenomenon  of  the  correlated  dependency  of  characters  and 
qualities  on  the  outer  conditions  of  life. 

E.      UNIT-CHARACTERS 

The  mechanism  of  an  organism  consists  of  numerous 
parts  which  are  more  or  less  exactly  fitted  to  one  another. 
Nearly  all  of  them  are  dependent  on  some  others  in  their 
development,  some  profiting  by  the  preponderance  of  these 
and  others  being  restricted  thereby.  Moreover  they  are 
governed  by  the  outer  conditions  of  hfe  and  these  influences 
change  some  of  them  in  the  same  direction  and  others  in  an 
opposite  one.  Thus  we  come  to  the  conception  of  a  general 
intcrdcpcndcncy  of  all  parts,  organs,  and  cpahties  of  an 
organism.  They  are  governed  more  or  less  by  the  same 
laws  wliich  cause  them  to  undergo  corresponding  changes 
when  subjected  to  the  same  influences. 

In  practice,  this  intcrdcpcndcncy  permits  the  indication 
of  valuable  f[ualitics  by  purely  botanical  marks,  and  gives 
the  possibility  of  basing  selection  upon  marks  wliich  may 
be  controlled  in  thousands  of  individuals  without  sacrificing 

O 

them  and  without  the  need  of  testing  all  of  them  directly  by 
their  economic  value.  It  is  an  important  principle  in  plant- 
breeding,  which  makes  the  work  more  rehable  and  more 
available  to  horticulturists  and  agriculturists  in  general.  Our 
great  admiration  for  men  of  genius  may  not  prevent  us  from 
deploring  that  the  improving  of  our  domestic  animals  and 


3IO  PLANT-BREEDING 

plants  should  be  laid  in  their  hands  only,  ^\'e  wish  to  know 
how  they  work,  and  how  their  great  achievements  are 
obtained.  We  wish  to  study  the  rules  and  laws  underlying 
their  attainments,  in  order  to  apply  them  to  as  many  instances 
as  possible. 

In  science,  on  the  other  hand,  the  innumerable  cases  of 
observed  correlations  lead  to  the  c[uestion  of  the  more  inti- 
mate causes  of  this  phenomenon.  Our  imagination  cannot 
be  content  with  the  outward  features  of  the  facts;  we  wish 
to  have  some  idea  of  their  innermost  nature.  In  this  hne  of 
thought  the  principal  difficulty  lies  in  the  absence  of  definite- 
ness  in  the  objects  we  have  to  deal  with.  We  speak  of 
correlation  and  interdependency,  but  we  have  no  idea  as 
to  what  the  things  are  that  should  be  related  to  or  depend- 
ent upon  each  other. 

Here  the  idea  suggests  itself  that  in  order  to  be  corre- 
lated the  characters  must  begin  by  being  independent  entities, 
which  through  some  later  means  may  come  into  relation  with 
others.  Perha])s  this  may  not  be  the  real  way  in  which 
nature  proceeds,  l)ut  at  all  events  it  is  the  way  in  which  we 
should  proceed  in  our  analysis.  Thus  we  come  to  the  con- 
ception of  unils  which  govern  and  control  the  visible  char- 
acters and  c[ualities. 

A  new  scope  for  investigation  is  opened  by  this  concep- 
tion. Each  organism  appears  to  us  as  a  microcosm,  con- 
sisting of  thousands  of  elemcntar}'  entities,  which  combine 
to  give  it  its  form  and  functions.  The  study  of  these  units 
encroaches  upon  systematic  and  comparative  sciences,  as 
well  as  upon  the  investigations  into  the  physiology  and  the 
evolution  of  all  living  beings.  All  comparison  culminates 
in  the  question  as  to  which  units  are  common  to  the  species 
under  discussion,  and  which  units  are  the  causes  of  their 
differences.  Systematic  affinity  is  reduced  to  the  same 
principle.     It  is  founded  on  the  community  of  a  more  or 


Fig.  96.  A.  The  pansv  and  some  of  its  parents.  B.  \'iola  lutea  grandi- 
flora.  C.  Viola  tricolor  versicolor.  D.  Viola  tricolor  lutescens.  After  Witt- 
rock. 


311 


312  PLANT-BREEDING 

less  large  number  of  units,  whilst  divergence  must  evidently 
be  the  result  of  the  occurrence  of  different  units.  The 
larger  the  number  of  common  units,  and  the  smaller  that  of 
varying  constituents,  the  greater  will  be  the  affmity. 

Wide  as  are  the  prospects  of  solving  the  most  difficult 
problems  of  systematic  science  and  comparative  investiga- 
tions, and  tempting  as  it  is  to  indulge  in  a  discussion  of  the 
possibility  of  the  discovery  of  their  ruling  laws  on  the  ground 
of  the  principle  of  units,  we  must,  of  course,  now  limit  our- 
selves to  questions  more  directly  concerned  with  our  inquiry. 

Among  these  the  chief  point  is,  what  is  to  be  considered 
as  a  unit?  This  question  is  intimately  connected  with  our 
main  subject,  and  sufficient  facts  are  at  hand  to  draw  at 
least  a  preliminary  sketch.  At  once  it  brings  us  upon  the 
ground  of  the  internal  causes  of  the  phenomena  of  correlation 
and  so  completes  the  scheme  made  by  our  distinction  be- 
tween these  and  the  external  factors. 

Our  units  may  be  considered  from  two  different  points 
of  view.  We  may  be  content  witli  analyzing  the  visible 
characters  and  with  reducing  them  to  independent  groups, 
or  we  may  ask  for  some  invisible,  although  material  cause, 
which  constitutes  the  real  source  of  each  unit.  This  latter 
inquiry,  however,  is  as  yet  wholly  of  a  hypothetical  nature, 
and  so  it  may  suffice  to  have  suggested  it,  and  to  return  to 
the  visible  features  for  our  further  chscussion. 

There  is  no  reason  for  assuming  that  a  unit  should  be 
limited  to  one  organ,  to  one  tissue,  or  to  one  cell.  Quite  on 
the  contrary,  it  seems  probable  that  a  unit  may  show  its 
activity  in  different  organs,  sometimes  even  in  almost  all  parts 
of  a  plant.  This  conception  aft'ords  a  broad  principle  for 
the  explanation  of  a  large  group  of  correlations,  the  corre- 
lated external  marks  being  simply  assumed  to  be  the  expres- 
sions of  the  same  internal  character.  The  faculty  of  pro- 
ducing a  red  or  blue  color  may  be  taken  as  an  instance.     If 


THE   ASSOCIATION    OF    CHARACTERS  ^13 

it  is  considered  as  a  unit,  the  tint  of  the  stems  and  foliage, 
and  that  of  tlie  corolla  and  all  other  parts  must  no  longer  be 
considered  as  so  many  separate  marks,  but  as  the  results  of  a 
single  intimate  character.  As  soon  as  this  is  lost,  or  reduced 
to  a  state  of  inactivity  by  the  production  of  a  pale  variety, 
it  becomes  a  matter  of  course  that  the  change  at  once  affects 
all  the  colored  organs,  as  we  have  seen  is  the  case  of  the  thorn- 
apple,  the  belladonna,  and  numerous  other  instances.  The 
same  explanation  holds  good  for  the  correlation  of  fissures, 
as  seen  in  the  petals  and  leaves  of  celandines  and  brambles. 
It  is  evidently  one  and  the  same  internal  unit  wliich  affects 
both  organs. 

If  this  principle  of  units  is  true,  it  must  have  an  over- 
whelming significance  in  the  study  of  hybridism.  In  the 
first  place,  all  the  modes  of  expression  of  one  unit  must  stead- 
ily keep  together,  whenever  the  entire  groups  of  characters 
are  thrown  into  one  another  in  crossing.  Tliis  rule  must 
hold  good  in  the  more  simple  cases  of  crossing  varieties  of 
the  same  species  as  well  as  in  the  hybrids  of  more  widely 
distant  parents.  In  the  first  case  the  rule  prevails  that  the 
hybrid  is  not  intermediate  between  its  parents,  but  bears 
the  characters  of  one  of  them.  Hybrids  between  blue  or 
red  flowered  species  and  their  white  varieties,  between  hairy 
and  smooth  forms,  between  spiny  and  unarmed  parents,  and 
many  other  instances  could  be  presented.  They  show  the 
marks  of  the  colored,  hairy,  or  spiny  parents  and  are  often 
not  at  all  distinguishable  from  these.  Here  the  unit  is  repro- 
duced without  being  weakened  or  rather  without  its  divergent 
expressions  being  separated  from  one  another.  The  second 
generation  of  the  hybrids  completely  supports  this  concep- 
tion. Some  plants  remain  true  to  the  type  of  the  first  gen- 
eration, but  others  return  to  the  alternative  grand-parent. 
Among  red-flowered  hybrids  whites  occur,  among  a  spiny 
and  hairy  progeny  some  smooth  ones  are  seen.     But  inter- 


Fig.  97.     (Gordon's  currant  (Ribcs  Gordonianiim),  a  hybrid  of  the  flowering 
currant  and  the  golden  currant. 


314 


Fig   08      A    The  flowering  currant  of  the  Pacific  Coast  (Ribes  sangui- 
■       neum).      B.  The  yellow  currant  {Ribes  aureim). 


315 


3i6  PLANT-BREEDING 

mediates  are  still  lacking,  showing  that  the  unit-character 
is  either  present  or  absent,  but  cannot  be  divided  into  lesser 
constituents. 

Such  spHttings  are  even  more  striking,  whenever  they 
are  produced  on  the  ditlerent  branches  and  flowers  of  the 
same  individual  plant.  The  instance  of  the  willow-leaved 
Veronica  has  been  dealt  with;  its  flowers  are  either  of  a  dark 
blue  or  completely  white,  the  unit  which  produces  the  dye 
being  wholly  absent  or  present,  ])ut  not  in  intermediate 
degrees.  A  parallel  case  is  that  of  the  hybrid  between  the 
orange  and  the  lemon,  which  may  show  the  separation  of 
its  units  within  the  same  fruits,  some  parts  having  the  color 
and  the  juice  of  the  orange  and  others  those  of  the  lemon. 

Crosses  between  species  are  more  difticult  to  understand. 
According  to  the  general  rule,  all  the  single  marks  of  the 
parents  are  mixed  up  in  the  offspring  so  as  to  form  c^uite  a 
new  type.  But  if  wc  look  more  closely  into  special  cases,  it 
is  often  possible  to  see  that  definite  units  of  the  parents  are 
recognizable  in  the  hybrids,  and  that  their  development  is 
often  the  same,  though  in  other  cases  checked  by  the  new 
combination.  A  notable  instance  of  this  rule  is  a  hybrid 
between  the  red  and  the  golden  currant  (Ribes  sanguineum 
and  R.  aureum),  wliich  is  commonly  cultivated  in  gardens 
under  the  name  of  Gordon's  currant  (R.  Gordonianum).  It 
has  the  form  and  hairiness  of  the  leaves  of  its  red  parent,  but 
in  the  flowers  the  red  and  golden  colors  are  combined  so  as 
to  give  an  intermediate  tinge.  The  combination,  however, 
is  not  at  all  perfect  and  easily  shows  on  petals  and  calyx,  its 
two  distinct  component  colors.  So  it  is  also  in  the  hybrid 
of  the  ordinar}'  and  the  yellow  foxgloves.  I  have  pollinated 
the  first  with  the  dust  of  the  second  and  had  a  beautiful  lot 
of  hybrids  which  flowered  richly  during  a  series  of  years. 
The  foHage  and  spikes  were  almost  those  of  the  yellow  parent, 
the  flowers  being  intermediate  in  size,  yellow,  but  with  a  red 


Fig.  99.  A.  The  cultivated  snapdragon.  B.-G.  Its  color  varieties. 
B.  Yellow.  C.  Delila,  tube  white  and  lips  red.  D-E.  Flesh-colored. 
F.  Brilliant,  of  a  fiery  red.  G.  Album,  white  with  a  yellow  spot  on  the 
lip.     H.  The  calyx  and  the  style  after  the  removal  of  the  corolla. 


317 


3i8  PLANT-BREEDING 

hue,  and  bearing  inside  the  corolla  numerous  spots  in  highly 
variable  numbers.  Such  spots  are  seen  in  both  the  parents, 
but  most  beautifully  de\x'loped  in  the  red  species.  Many 
other  instances  could  be  given.  The  hybrid  of  the  common 
and  the  small-flowered  evening  primroses  (OEnothera  biennis 
and  (En.  muricata)  has  the  flowers  of  one  and  the  spikes  of 
the  other  parent.  In  the  culitivated  violets  the  size  and  yel- 
low tinge  are  derived  from  one  of  the  parents,  the  Viola 
lutea  grandiflora,  and  so  on. 

As  a  rule  some  characters  of  one  or  the  other  parent  may 
be  more  or  less  easily  recognized  in  the  hybrid,  but  others 
are  so  intricately  mingled  that  our  knowledge  is  wholly  insuf- 
ficient to  single  them  out.  Each  of  them  may  be  impeded 
in  its  development  by  the  others,  and  as  long  as  we  do  not 
understand  the  laws  by  which  such  mutual  hindrances  arc 
governed,  it  is  impossible  to  give  more  than  a  superficial 
analysis. 

Crosses  may  give  us  an  insight  into  the  nature  of  unit- 
characters  in  still  another  way.  Many  so-called  characters 
are  in  reaUty  composite  entities  and  it  is  by  means  of  crossing 
that  they  can  be  divided  into  their  constituent  units.  As 
an  instance  I  select  the  color  of  the  flowers  and  especially 
that  of  the  cultivated  snap-dragon  (Antirrhinum  majus). 
Its  large  and  bright  corollas  strike  our  eyes  b}  their  fiery 
red,  and  on  a  closer  inspection  show  a  yellow  spot  on  the 
under  lip,  and  a  paler  tinge  on  the  tube.  These  deviations 
from  the  general  color  may  be  considered  as  indications  of 
its  composite  nature.  Besides  this  species  a  white  variety 
is  largely  cultivated.  It  is  not  absolutely  white,  but  lacks 
the  red  dye  and  the  yellow  tinge  of  the  main  parts.  The 
yellow  spot  on  the  under  lip,  however,  has  not  disappeared, 
but  is  still  \asible,  and  almost  as  well  developed  as  in  the 
red  species.  Here  we  have  the  first  proof  of  the  build- 
ing up   of    the   original   type  out  of   more  simple  constit- 


Fig.  lOO.     Danebrog   opium    poppy;    petals 
red  with  a  large  white  spot  at  the  base. 


319 


320  PLANT-BREEDING 

ucnts,  since  the  yellow  spot  is  evidently  due  to  a  separate 
unit. 

If,  now,  we  cross  the  red  and  the  white  types,  we  get, 
according  to  the  ordinary  rules,  hybrids  that  bear  the 
marks  of  the  species  and  not  those  of  the  variety.  But  in 
the  second  generation  a  spHtting  occurs,  and  it  is  tliis  spht- 
ting  which  frees  the  units  from  one  another.  A  complete 
analysis  has  not  as  yet  been  made,  but  some  constituents 
have  been  separated  and  have  proven  to  be  real  units.  Of 
course,  only  some  of  the  hybrids  have  but  one  unit  in  a  pure 
condition,  others  having  groups  of  two  or  three  or  even  more 
of  them  in  all  imaginable  combinations.  But  the  more 
simple  forms  are  easily  recognizable  among  the  throng.  In 
the  first  place  they  give  proof  of  the  independence  of  the  red 
and  yellow  colors.  A  pure  yellow  form  exists,  lacking  all 
of  the  red.  It  has  two  units  of  color,  the  one  being  the  spot 
on  the  under  hp,  already  mentioned,  and  the  other  the  general 
tinge.  The  red  dye  is  also  produced  by  at  least  two  units, 
one  of  them  being  a  fleshy  color,  equally  distributed  in  all 
parts  of  the  corolla,  except  the  yellow  spot,  and  the  other 
being  of  a  bright  color,  but  limited  to  the  lips.  It  is  a  type 
called  DeHla,  and  distinguished  by  its  colorless  tube.  As 
is  easily  seen,  the  combination  of  these  two  units  gives  the 
dark  lips  and  the  pale  tube  of  the  original  species,  and  this 
not  only  theoretically  but  also  experimentally  whenever  the 
two  constituents  are  combined  by  crossing. 

In  the  same  way  the  colors  and  color-designs  of  other 
flowers  may  be  analyzed  and  their  component  units  sepa- 
rated. The  most  obvious  means  for  almost  all  cases  is  the 
crossing  of  the  species  which  has  all  the  units,  with  the  white 
variety  in  which  they  arc  al^sent  or  at  least  latent.  Such 
crosses  usually  result  in  the  desired  splitting.  A  most  beau- 
tiful instance  may  now  be  mentioned.  It  is  the  separating 
of  the  dark  central  spot  of  the  opium-poppies  from  the  red 


THE  ASSOCIATION   OF   CHARACTERS  321 

of  the  upper  part  of  the  petals.  It  produces  the  variety 
known  as  the  Danish  flag  and  characterized  by  its  broad 
central  wliite  cross  on  the  red  field  of  the  petals. 

It  goes  without  saying  that  these  splittings  may  not 
only  be  produced  by  artificial  crosses,  but  must  occur  also 
whenever  accidental  crosses  are  brought  about  by  insects 
visiting  the  variety  and  the  species  when  cultivated  side  by 
side.  If  this  takes  place  in  a  nursery,  the  horticulturist  will 
recognize  the  new  types,  isolate  them  as  such,  and  put  them 
on  the  market.  They  will  prove  constant,  or  at  least  become 
so  after  some  additional  spHttings.  In  other  words,  many 
intricately  colored  species  must  afford,  besides  their  white 
variety  a  larger  or  smaller  number  of  types,  in  wliich  the 
constituents  of  their  color-designs  are  more  or  less  com- 
pletely isolated.  By  this  means  we  can  study  the  units  by 
simply  cultivating  and  comparing  all  the  commercial  varie- 
ties of  such  a  species. 

Having  thus  mentioned  the  chfferent  methods  by  which 
unit-characters  may  become  isolated,  in  order  to  give  proof 
of  their  real  existence,  we  now  come  to  the  other  side  of  the 
c|uestion.  Our  conception  of  units  was  originally  based  on 
the  desire  of  having  some  principle  wliich  might  explain 
the  internal  causes  of  correlation,  or  at  least  some  of  them. 
We  have  seen  that  botanical  marks  observed  in  the  scales 
of  an  ear  of  wheat  or  barley  may  be  incUcations  of  hardiness 
in  winter,  of  fitness  for  definite  commercial  purposes,  of 
resistance  to  diseases,  and  other  valuable  quahtics.  In  order 
to  explain  such  coincidences,  we  have  assumed  that  unit- 
characters  are  not  productive  of  single  marks,  but  may  ex- 
Mbit  their  influence  in  different  parts  of  the  plant  body. 
The  same  unit  may  become  visible  in  the  color  of  the  stem, 
foliage,  flower,  and  fruit,  and  so  it  must  also  be  with  other 
units,  which,  when  added  to  a  type,  not  only  change  its 
flowers  or  its  leaves,  but  also  aft"cct  other  organs,  physiologi- 


322  PLANT-BREEDING 

cal  qualities,  and  perhaps  even  the  whole  mode  of  growth 
and  development. 

But  if  we  wish  to  give  a  direct  proof  of  this  assertion, 
comparative  study  is  no  longer  sufficiently  reUable.  Its 
units  arc  in  reahty  hypothetical.  Their  existence  may  seem 
to  be  cjuite  obvious  and  to  be  in  no  need  of  further  proof,  but 
as  soon  as  they  are  to  become  the  basis  for  far-reaching  con- 
clusions they  ought  to  be  beyond  all  reasonable  doubt. 

Our  question  is,  when  one  unit  is  added  to  or  subtracted 
from  a  well-known  type,  what  are  the  changes  which  are 
thereby  produced?  Now  such  an  adchtion  or  subtraction  is 
exactly  what  we  call  a  mutation,  and  thus  it  becomes  evident 
that  only  directly  observed  mutations  can  give  a  reliable 
answer.  Moreover,  mutations  are  so  rare  that  the  chance 
of  two  of  them  occurring  together  seems  too  small,  or,  in 
other  words,  that  we  may  confidently  assume  that  each  single 
mutation  affects  only  a  single  unit. 

Considering  the  mutations  of  the  evening  primroses  from 
this  point  of  view,  our  conception  of  the  correlative  nature 
of  the  different  changes  which  each  of  them  produces  will 
at  once  become  clearer  in  its  meaning  and  win  the  rank  of 
full  experimental  proof.  Some  of  them  are  more  easily  de- 
scribed and  understood  than  others,  but  the  same  general 
rules  prevail  in  nearly  every  single  case. 

Let  us  begin  with  the  short-styled  variety  or  (Enothera 
brevistylis.  Its  mutative  origin  has,  as  a  fact,  not  been  direct- 
ly observed,  but  may  be  deduced  from  its  occurrence  on  only 
one  native  locahty  and  amidst  an  overwhelming  throng  of 
normal  primroses.  The  unity  of  its  character,  has,  on  the 
other  hand,  been  proven  by  its  behavior  in  crosses  with  the 
parent  species.  The  characteristic  mark  of  tliis  variety  Hes 
in  the  short  style  which,  instead  of  pushing  the  stigmas 
above  the  anthers,  hardly  reaches  the  throat  of  the  tube. 
Other  marks  are  correlated  with  this.     In  the  first  place, 


^ 


f 


.^■*^ 


.if. 


323 


324  PLANT-BREEDING 

some  characters  of  the  flower  are  affected,  and  in  the  second 
place,  some  of  the  leaves.  In  the  flowers,  the  stigma  is  broad- 
ened and  flattened  and  less  regularly  divided  into  its  four  parts. 
The  ovary,  which  is  inferior  in  the  normal  species,  is  here 
only  partially  so,  and  its  cavities  are  seen  to  protrude  above 
the  insertion  of  the  calyx  tube,  occupying  thereby  the  basal 
part  of  the  style.  How  these  changes  may  be  Ijrought  about 
by  the  same  cause  that  shortens  the  style,  we  do  not  under- 
stand. But  far  less  can  we  guess  the  connection  between 
the  marks  of  the  flowers  and  the  foliage.  The  leaves  of  the 
brevistylis  have  more  rounded  tips  and  the  plants  may,  by 
this  means,  be  recognized  weeks  before  the  development  of 
the  flower  buds,  and  sometimes  even  in  the  rosette  stage. 
This  instance  of  correlation  seems  analogous  to  the  facts 
observed  among  cereals  and  other  cultivated  plants.  We 
can  only  acknowledge  the  fact  from  the  regularity  of  the 
occurrence  of  the  combination,  without  even  being  able 
to  guess  its  cause. 

Of  course,  there  are  also  correlations  which  we  may 
understand  or  at  least  believe  we  understand.  In  our  case, 
one  of  these  is  seen  in  the  broader  flower-buds  of  the  (E.  brev- 
istylis, when  compared  with  the  CE.  Lamarckiana.  In  the 
latter  the  calyx  is  extended  by  the  growth  of  the  style,  which 
presses  the  stigma  from  within  against  its  tip.  The  calyx 
being  thereby  elongated,  it  is  only  natural  that  its  form  be- 
comes more  conical  as  soon  as  the  long  style  is  absent.  Per- 
haps another  mark  may  be  explained  in  a  similar  way.  At 
the  time  of  the  ripening  of  the  seeds  the  (E.  brevistyhs  is 
easily  recognized  by  its  very  small  pods,  containing  hardly 
any  seed.  It  may  be  assumed,  although  a  direct  proof  is 
wanting,  that  the  elongation  and  narrowing  of  the  ovarial 
cavities  within  the  base  of  the  style  is  an  impediment  to  the 
growth  of  the  pollen-tubes,  and  thus  liindcrs  a  normal  fertil- 
ization. 


Fig.  I02.  A.  The  short-styled  Evening-primrose.  B-F.  Its  parent  form. 
b.  A  ilower  after  the  removal  of  part  of  its  petals  and  stamens,  c.  The 
same  without  petals,  d.  The  same  without  the  tube  and  the  caly.x.  e.  A 
flowerbud.  /.  Ripe  fruits.  B-F.  The  corresponding  parts  of  the  parent 
species,  g.  Styles,  h.  Longitudinal  section  of  ovary,  i.  Transversal 
section  of  base  of  stvle  and  calvx-tubc. 


325 


326  PLANT-BREEDING 

Exactly  similar  conclusions  may  be  derived  from  a  dis- 
cussion of  the  (Enothera  lata,  which  has  often  been  seen  to 
be  produced  from  the  parent  species  by  a  single  leap.  There 
is  even  less  connection  between  the  various  marks  by  wliich 
it  is  distinguished  from  Lamarck's  primrose.  It  strikes  us 
through  all  the  periods  of  its  life  as  quite  another  type.  The 
very  first  leaves  of  the  }oung  seedlings  differ,  being  broader 
and  more  rounded  at  the  tip.  This  type  of  leaves  is  pre- 
served during  the  whole  life  history,  and  the  rosettes,  the 
young  stems,  and  the  branches  are  distinguished  by  this 
same  mark.  There  can  be  no  doubt  that  the  form  of  the 
leaves  during  the  whole  lifetime  is  regulated  by  one  single 
unit-character.  Tliis  unit  probably  causes  still  another 
mark,  the  extremely  sinuous  surface  of  the  leaves.  Sinuos- 
ities, although  not  lacking  in  the  parent  species,  are  much 
more  numerous  in  this  mutant  form.  The  weakness  of  the 
stems  and  the  consequent  bending  of  their  tips  is  more  diffi- 
cult to  explain  as  an  effect  of  the  same  cause,  but  it  is  as 
constant  a  mark  as  the  leaves.  More  curious  is  the  behavior 
of  the  flowers.  These  have  only  one  sex,  producing  no 
pollen  at  all.  The  anthers  are  developed  and  of  the  normal 
size,  but  in  their  cavities  the  pollen  is  sometimes  entirely 
wanting,  and  sometimes  sterile,  their  place  being  occupied 
by  the  outgrowth  of  the  cells  of  the  inner  layer  of  the  wall. 
These  cells  commonly  collapse  and  are  absorbed,  and  so  it 
is  in  Lamarck's  primrose  and  in  all  its  other  derivatives,  but 
in  the  lata  they  thrive  and  increase  their  size  until  the  time 
of  the  shriveling  of  the  anthers. 

The  correlation  between  the  broad  and  sinuous  leaves 
and  tliis  inabiUty  to  produce  pollen  is  a  phenomenon  wliich 
it  is  at  present  far  beyond  our  power  to  explain.  But  it  is 
absolutely  constant.  The  lata  has  been  produced  anew  by 
the  main  strain  in  my  garden  more  than  three  hundred  times. 
A  large  number  of  these  plants  have  flowered,  and  the  flowers 


w~"— 

-^ 

tk 

M 

jjffiwFjB^ 

Yiil.   lo: 


A    Ijirntiial    specimen    of    the    Evening- 
primrose  of  Lamarck. 

327 


328  PLANT-BREEDING 

have  always  borne  the  same  marks,  especially  the  same 
deficiency  of  the  pollen.  This  can  be  predicted  with  abso- 
lute security  from  the  single  inspection  of  the  first  leaves 
of  the  young  seedUngs. 

Here  we  have  the  full  duphcate  of  so  many  cases  of  ob- 
served correlations,  with  which  we  have  previously  dealt. 
But  in  this  case  the  repeated  observation  of  the  origin  by  a 
single  leap  may  be  considered  as  a  direct  experimental  proof 
of  what,  in  other  cases,  can  be  derived  only  from  comparative 
studies.  In  such  a  case  no  chance  coincidence,  no  depen- 
dency on  similar  outer  conditions  of  life,  and  no  other  hypoth- 
esis can  ade([uately  explain  the  facts.  Only  the  assumption 
that  one  unit-character  may  affect  different  organs  of  the  plant 
in  different  and  apparently  independent  ways  gives  a  sufti- 
cient  idea  of  their  internal  connection. 

The  same  correlations  may  be  seen  in  most  of  my  other 
mutants.  The  scintillans  and  the  oblonga  are  small  types, 
recognizable  in  their  youth  by  their  narrow  leaves.  The 
albida  is  whitish  and  very  deHcate  and  has  its  pecuhar  shape 
of  spikes  and  flowers.  The  kcvifolia  combines  smooth 
leaves  with  a  propensity  for  reducing  the  petals  on  the  weaker 
branches  to  an  ovate  form.  But  the  most  interesting  instance 
and  the  one  which  almost  exactly  corresponds  to  the  corre- 
lation between  botanical  and  practically  valuable  characters 
of  the  agricultural  crops  is  that  of  the  CEnothera  gigas.  Its 
botanical  marks  are  the  dense  f  oh  age,  the  large  flowers,  the 
swollen  flower-buds,  and  the  small,  but  thick  pods  \\ath  their 
less  numerous,  but  bigger  seeds.  Its  cultural  feature  is  its 
great  tendency  to  be  biennial.  The  parent  species  and 
most  of  its  other  derivatives  can  easily  be  cultivated  as  an- 
nuals, and  the  rubriner\is  evidently  prefers  this  condition. 
On  the  other  hand,  the  gigas  prefers  to  develop  its  stems  only 
in  the  second  year.  Under  the  conditions  existing  in  my 
experimental  garden,  it  ordinarily  defies  all  endeavors  to 


Fig.  104.     Spikes  with  almost  ripe   fruits  of  A.  Oenothera  gigas,  a  mutant 
species.     B.  Oenothera  Lamarckiana,  its  parent  form. 


329 


330 


PLANT-BREEDING 


make  it  flower  and  produce  seeds  in  its  first  year.  Ordina- 
rily at  least  one  half  of  the  plants  remain  in  the  rosette  stage, 
the  remainder  producing  their  stems  only  late  in  summer 
or  towards  the  fall,  and  thus  having  hardly  time  enough  to 
display  their  flowers,  and  none  at  all  to  ripen  their  fruits. 


^Ij^^            ^«  - 

A 

3 

Fig.  105.  A.  A  rosette  of  rootlcaves  of  Lamarck's  Evening-primrose 
in  September.  B.  A  similar  rosette  of  one  of  its  mutants  (OfH.  Jc/«////a«5) 
in  the  same  age. 

Only  in  some  very  favorable  years  have  I  succeeded  in  saving 
seed  from  annual  gigas  plants. 

Here  we  have  an  instance  of  correlation  such  as  that 
between  hairiness  or  form  of  scales  and  hardiness  in  winter 
or  resistance  to  diseases.  But  here  the  mutative  origin  of 
the  type  affords  a  direct  proof  of  the  vaUdity  of  our  assump- 
tion that  such  divergent  quaUties  may  be  the  effects  of  the 
same  internal  unit-characters. 


Fig.  io6.  The  smooth-leaved  variety  of  the  Evening-primrose  (Oeno- 
thera laevijolia).  a.  A  side-flower  with  ovate  instead  of  obcordate  jjetals, 
one  of  the  new,  highly  variable  characters  of  the  new  form. 

331 


332  PLANT-BREEDING 

By  this  means  the  direct  observation  of  mutations  sup- 
ports the  conchisions  derived  from  purely  comparative  in- 
vestigations. Together  tliey  teach  us  the  great  hiw  of  correl- 
ative variability,  by  which  one  and  the  same  internal  cause 
may  affect  different  organs  and  ciuaHties  in  widely  divergent 
ways.  This  law  intimately  connects  the  scientific  results 
and  methods  of  selection  now  in  use  at  the  Swedish  experi- 
ment station  at  Svalof  with  the  principles  and  achievements 
of  Burbank  in  horticultural  practice  and  with  numerous 
other  more  or  less  isolated  scientific  facts  and  methods  of 
practice.  It  points  out  the  lines  for  further  investigation. 
The  study  of  correlations  must  be  carried  on  on  the  broadest 
possible  basis.  Alinute  and  apparently  small  marks  must 
be  analyzed  and  compared  with  valuable  properties.  Every- 
where connections  will  be  discovered.  Some  of  them  may 
be  accidental  coincidences,  and  of  no  further  significance, 
but  others  will  hold  good  through  large  numbers  of  instances. 
From  the  broadest  possible  knowledge  of  these,  new  princi- 
ples of  selection  will  be  derived,  and  slowly,  but  surely,  we 
shall  approach  a  definite  knowledge  of  the  meaning  of  much 
that  is  as  yet  hidden  from  our  eyes.  Then  we  shall  see  that 
there  is  no  mystery  connected  with  the  indications  which 
seedlings  give  concerning  the  fruits  they  will  bear  in  later 
years. 


VI 

THE    GEOGRAPHICAL   DISTRIBUTION    OF 
PLANTS 

Among  all  sciences,  that  of  the  geographical  distribution 
of  animals  and  plants  is  necessarily,  perhaps,  the  most  inter- 
national. In  crossing  the  continent  of  America  in  order 
to  reach  the  much  beloved  far  West,  my  eye  was  struck  by 
the  cHversified  conditions  under  which  vegetation  and  agri- 
culture must  thrive.  Arid  deserts  and  lofty  mountains 
contrast  with  humid  and  fertile  plains,  with  large  forests 
and  great  rivers,  with  marshes  and  lakes.  Each  of  these 
can,  of  course,  be  compared  with  some  parts  of  Europe,  and 
though  the  impression  we  get  is  that  of  essential  difference, 
the  separate  parts  are  as  a  fact  only  a  repetition  of  what  is 
seen  with  us. 

The  cause  of  the  cUversity  is,  therefore,  not  to  be  sought 
in  the  cHmatic  conchtions,  but  rather  in  the  special  character 
of  the  vegetation.  In  American  agriculture  corn  has  taken 
the  place  which  in  Europe  is  given  to  the  smaller  cereals. 
So  it  is  also  in  nature.  Everywhere  the  European  "traveler 
sees  new  types  and  new  kinds.  As  a  rule  they  catch  his  eye 
by  some  common  features  which  are  strange  to  him.  Among 
these,  I  mention  only  the  rich  colors  of  the  flowers  in  sum- 
mer and  of  the  foHagc  of  trees  and  shrubs  in  the  fall. 

We  are  thus  impressed  with  one  of  the  great  principles 
of  the  geographical  distribution  of  Hving  organisms.  We 
are  convinced  that  the  fundamental  difference  between  the 
organic  beings  of  the  two  great  continents  is  not,  in  the  main, 
due  to  their  cHmates  and  soils,  but  that  it  can  have  no  other 
cause  than  their  separate  origin  from  the  organisms  that 
peopled  them  in  previous  geological  times.  One  of  the  best 
proofs  of  the  truth  of  this  principle  is  given  by  some  of  the 

333 


334  PLANT-BREEDING 

most  common  plants  of  the  fields  and  waste  places  in  Cali- 
fornia. Immigrants  from  Europe  are  of  common  occurrence, 
and  some  plants  have  spread  with  a  most  astonishing  rapid- 
ity. The  Napa-tliistle  (Centaurea  MeUtensis)  and  the  wild 
chamomile  (^latricaria  Chamomilla)  are  the  most  obvious 
instances,  but  many  other  introduced  species  could  be  ad- 
duced. 

It  is  evident  that  such  new  plants  are  finding  conditions 
here  which  suit  them  as  well  and  perhaps  better  than  those 
under  which  they  Uve  in  Europe.  The  same  phenomena 
are  afforded  by  other  species  which  have  been  introduced 
from  America  into  Europe,  and  are  now  common  weeds  or 
even  dreaded  pests  with  us.  The  Canadian  water  pest,  or 
Elodea  canadensis  and  the  American  Azolla  (A.  carolinen- 
sis)  are  now  perhaps  the  most  widely  dispersed  obnoxious 
plants  of  our  canals  and  ditches,  occurring  in  the  largest 
numbers  of  individuals. 

Such  observations  are  apt  to  awaken  doubts  as  to  the 
real  value  of  the  current  ideas  concerning  the  nature  of  the 
adaptations  of  the  organisms  to  their  environment.  The 
Napa-thistle  and  the  wild  chamomile  are  evidently  as  well- 
fitted  for  the  CaUfornian  soil  and  climate  as  any  of  its  own 
native  plants.  Notwithstanding  this,  they  have  acrjuired 
the  quahties  wliich  enable  them  to  multiply  in  such  stupen- 
dous numbers  here,  in  another  country.  Whether  in  their 
native  localities  the  soil  and  the  climate  were  the  same,  we 
do  not  know,  but  we  may  confidently  assume  that  their 
living  environment  was  different,  inasmuch  as  it  must  have 
consisted  of  European  plants  and  animals.  And  it  is  gener- 
ally conceded  that  lixdng  nature  has  a  larger  influence  on  the 
evolution  of  new  species  than  the  purely  physical  and  chem- 
ical conditions. 

Our  doubt  is  tliis:  Are  the  native  plants  of  California 
still  hvincj  under  the  same  influences    under  which  thev 


GEOGRAPHICAL   DISTRIBUTION   OF   PLANTS     335 

originated?  If  this  were  so,  we  might  assume  that  tlieir 
fitness  for  their  present  Hfe-conditions  has  been  acquired  by 
means  of  adaptation.  If  not,  there  is  no  reason  at  all  for 
explaining  their  characters  on  the  basis  of  this  principle,  and 
all  speculations  of  tliis  Idnd  are  reduced  to  mere  hypotheses, 
lacking  even  the  possibiHty  of  comparative  or  experimental 
evidence. 

The  current  conception  tacitly  assumes  that  all  or  nearly 
all  living  beings  originated  on  the  very  spots  where  they  are 
now  found,  or,  at  least,  under  c|uite  similar  conditions.  It 
is  evident  that  only  on  this  assumption  the  causal  connec- 
tion between  environment  and  characters  can  help  us  in  ex- 
plaining the  latter.  The  present  Hfe-conditions  are  called 
upon  to  explain  the  observed  instances  of  fitness  in  plants. 

If,  however,  plants  have  as  a  rule  migrated  from  their 
native  spots,  then  they  are  now  found  in  environments  wliich 
have  no  right  whatever  to  be  considered  as  the  cause  of  their 
characters.  Quite  on  the  contrary,  the  migration  and  the 
dispersion  must  have  been  guided  by  the  nature  of  the  species. 
Or,  in  other  words:  Each  plant  must  have  sought  out  the 
conditions  where  it  could  thrive  best  on  account  of  its  given 
peculiarities. 

Thus  we  come  to  the  conclusion  that  the  relation  between 
organisms  and  their  present  environment  is  quite  the  reverse 
of  what  it  is  commonly  assumed  to  be.  The  properties  of 
the  animals  and  plants  must  be  considered  as  given  facts, 
and  on  the  l)asis  of  these  their  present  distribution  is  to  be 
explained.  It  is  readily  granted  that  this  proposition  only 
withdraws  the  main  point  from  our  study,  but  on  the  other 
hand  it  brings  the  investigation  along  a  path  of  direct 
inquiry  and  experience  instead  of  imperfectly  founded 
speculations. 

From  tliis  point  of  view  the  geographical  distribution 
of  plants  and  animals  must  be  discussed  under  two  different 


336  PLANT-BREEDING 

headings.  One  case  embraces  the  widely-spread  species, 
the  other  those  with  a  hmitcd  area.  For  the  first  it  is  instantly 
clear  that  at  best  only  one  of  their  numerous  habitats  can  be 
the  spot  where  they  have  originally  been  produced.  To  all 
their  other  locaHties  they  must  have  been  introduced,  and,  if 
we  do  not  consider  collective  forms  but  pure  and  elementary 
types,  this  must  have  happened  without  changing  their 
original  characters.  Now,  the  (piestion  arises,  which 
locahty  is  their  native  one?  Observation  teaches  that 
in  almost  all  instances  there  is  no  evidence  of  a  difference 
between  this  one  and  the  others.  Therefore,  it  is  simply 
impossible  to  answer  this  c|uestion  in  any  case  with  sufficient 
certainty.  It  is  generally  assumed  that  in  the  center  of  the 
whole  dominion  of  a  plant  its  native  station  is  concealed, 
but  this  is  only  a  hypothesis,  resting  on  no  observational 
basis.  Quite  as  v.'ell  some  species  might  have  spread  in  one 
direction  only,  and  then  their  native  spot  would  he  at  the 
very  end  of  their  realm.  Granting  that  we  cannot  recognize 
this  original  center  of  dispersion,  we  may  turn  to  a  discussion 
of  the  large  majority  of  the  observed  locahties.  Some  plants 
are  evidently  better  fitted  for  certain  stations,  while  others 
prefer  different  life-conditions.  The  large  group  of  the 
evening  primroses  may  afford  instances.  In  California 
only  one  large- flowered  species  is  met  with  in  the  wild 
state.  It  is  the  CEnothera  Hookeri  which  occurs  on  waste 
places  along  roads  and  railroads,  and  may  even  be  seen  here 
and  there  in  the  parks.  It  is  evidently  suited  to  the  chmate  of 
CaUfornia,  but  its  dispersion  in  Arizona  and  other  neighbor- 
ing states  makes  it  ven^  probable  that  it  is  no  real  native 
Californian,  but  has  only  been  introduced.  In  tliis  case  no 
single  one  of  its  quahties  can  possibly  be  explained  by  the 
demands  of  its  present  environments. 

Other  species  of  evening  primroses  give  further  proofs. 
Two  of  them  were  introduced  into   Europe   more  than    a 


Fig.  107.     Oenothera  muricata,  a  seaside  plant,  which  originated  far  from 

the  sea. 
337 


338  PLANT-BREEDING 

century  ago,  and  have  spread  widely  over  various  countries. 
Both  have  become  quite  common  with  us,  but  prefer  dif- 
ferent life-conditions.  Now  it  is  very  interesting  to  note 
that  one  of  them,  the  small- tlowered  form  or  CEnothera 
muricata,  ]3refers  the  proximity  of  the  sea-shore,  whilst 
the  common  species  or  (E.  biennis  prefers  inland  fields  and 
places.  On  the  sand-dunes  along  the  coast  of  Holland,  this 
difference  in  stations  is  very  striking,  the  small  flowering 
type  being  almost  limited  to  a  region  of  a  few  miles  along  the 
coast. 

How  can  this  noticeable  difference  be  explained  ?  Espe- 
cially, how  did  the  muricata  accjuire  its  love  for  the  sea-air 
and  the  sea- winds?  All  our  knowledge  of  the  dispersion 
of  the  evening  primroses  points  to  some  part  of  the  middle 
states  of  the  United  States  of  America  as  their  original 
habitat,  and  so  it  seems  evident  that  even  the  muricata  was 
originally  an  inland  plant,  springing  up  far  from  any  influence 
of  the  sea. 

From  this  special  instance  we  may  conclude  that  at  least 
in  many  cases,  the  geographical  distribution  of  wide-spread 
plants  is  governed  by  quahties  acquired  quite  independently 
of  their  present  life-conditions.  Innate  propensities  govern 
their  dispersion,  and  have  determined  where  they  should  be 
crowxled  out  and  where  they  could  multiply  themselves. 
In  order  to  make  this  conclusion  still  more  convincing,  I 
might  draw  your  attention  to  the  chronological  side  of  the 
question.  VVe  are  trying  to  explain  the  constitution  of 
forms  on  the  ground  of  the  conditions  under  wliich  they 
are  now  living.  But  in  doing  so,  we  forget  how  very  old 
they  are,  and  how  much  nature  may  have  changed  since 
their  first  origin.  ]\lany  of  our  most  common  species  are 
known  to  be  older  than  the  glacial  periods,  their  fossil 
remains  being  found  in  the  upper  tertiary  deposits  (e.  g. 
Statiotes    aloides).     If    they    have    endured    these    dreadful 


Fig.  loS.     Wulfenia  carinthiaca,  -tthich  grows  only  on  the  Gartnerkugel  in 

Carinthia. 


339 


340  PLANT-BREEDING 

times  of  cold  and  of  subsequent  repeated  migration,  how 
can  we  know  under  what  circumstances  they  originated? 
Observation  teaches  wliich  of  tlie  life-conditions  available  at 
the  present  time  are  the  best  suited  for  them,  but  there  is 
no  reason  to  assume  that  they  have  been  produced  under 
similar  ones.  Plants  originally  inland  forms  may  now 
prefer  the  sea-shore,  because  they  are  crowded  out  else- 
where, and  many  an  alpine  plant  would  without  doubt 
prefer  a  lower  and  warmer  region  were  it  not  for  dread  of 
the  enemies  it  has  to  meet  there. 

Opposed  to  the  common  plants,  which  have  evidently 
migrated  far  from  their  place  of  birth,  are  the  so-called 
local  species,  which  inhabit  only  one  mountain,  or  one  valley, 
or  arc  Hmited  even  to  the  slope  of  a  single  hill.  Here, 
at  first  sight,  two  possibiUties  occur.  The  species  may  be 
of  recent  origin,  and  may  not  as  yet  have  found  time  for 
spreading  itself  outside  of  its  native  spot.  Or  it  may  be 
old,  perhaps  slowly  dying  out.  In  this  case  it  may  once  have 
been  distributed  o\er  large  areas,  but  have  disappeared 
from  almost  all  points.  Only  there  where  it  enjoyed 
suthcient  isolation  or  sufficiently  suitable  life-conditions 
has  it  survived.  The  study  of  these  conditions  may  then 
show  us  the  minimum  of  reciuirements  for  continuing  its 
existence,  but  it  does  not  tell  in  any  way  how  these  precious 
qualiti'js  may  have  originated.  Who  does  not  remember  the 
description  of  the  bright  dark-blue  Wulfenia,  as  given  by 
Ouida  in  her  "Moths"  (II  271),  when  Correze  brought 
this  rare  plant  from  the  almost  inaccessible  heights  of  the 
Gartnerkugel  in  Carinthia  ?  There  it  grows  upon  the  slopes 
of  the  mountain,  and  nowhere  else  in  all  the  world  is  it 
found.  Evident!}'  it  is  only  a  reUc  of  times  that  have  passed 
away. 

How  can  we  determine  whether  in  any  given  case  a 
local  species  is  nearer  its  origin  than  its  decline?     In  most 


Fig.    109.     The    smooth-leaved    campion,    a 
local  plant  of  Hungary  with  a  useless  character. 


341 


342  PLANT-BREEDING 

cases,  the  question  is  difficult  to  decide,  but  there  is  one 
instance  in  wliich  most  authors  agree  in  acknowledging 
the  youth  of  the  type.  Tliis  is  the  case  of  the  local  types 
of  those  polymorphic  species,  whose  numerous  elementary 
forms  inhabit  different  stations,  but  are  collected  together 
in  the  same  region.  Here  the  relations  between  hfe-con- 
ditions  and  characters  may  be  studied,  and  the  question 
may  be  answered  on  what  qualities  the  occurrence  on  the 
observed  spots  depends.  Two  instances  may  be  given, 
since  they  are  illustrative  of  the  real  nature  of  the  question. 
One  is  a  smooth  variety  of  the  ordinary  campion,  which  is 
found  only  in  a  grove  near  Miinchengratz  in  Southern 
Hungary  (Lychnis  Preshi).  Here  it  grows  abundantly. 
But  there  is  no  imaginable  connection  between  this  mountain- 
slope  or  its  forest  and  the  lack  of  hairs  on  the  leaves  of  the 
local  campion.  No  other  explanation  seems  possible  than 
that  of  an  accidental  mutation,  which  changed  a  character 
in  a  harmless  way  and  thus  left  the  chances  of  survival  for 
the  new  variety  simply  the  same  as  they  were  for  the  species 
itself.  The  other  case  is  that  of  two  alpine  species  of  milfoil. 
They  are  nearly  similar  in  botanical  marks,  even  to  such  a 
degree  that  their  differences  may  easily  be  o\'erlooked. 
They  are  different,  however,  in  their  demands  on  the  chem- 
ical constituents  of  the  soil,  the  one  preferring  calcareous 
and  the  other  silicious  formations.  The  Achillea  moschata 
prefers  the  hmy  and  the  A.  atrata  the  siliciferous  slopes. 
In  Switzerland  wherever  both  species  occur  in  the  same 
valley  they  are  strictly  limited  to  their  particular  kind  of 
soil,  the  one  form  wholly  excluding  the  other.  But  as  soon 
as  only  one  species  occurs  in  a  valley,  it  is  indifferent  to  the 
nature  of  the  soil  and  grows  on  hme  as  well  as  on  silica. 
Now,  how  can  we  tell  whether  they  have  originated  separately, 
each  on  the  soil  which  is  now  best  for  it,  or  whether  they 
had  a  common  origin  and  have  only  spread  afterward,  each 


Fig.  no.     Two  Alpine  species  of  milfoil.     A.  The  .\chillca  atrata 
of  calcareous  soils.    B.  The  A.  moschata  of  siliciferous  soils. 


343 


344  PLANT-BREEDING 

multiplying  itself  most  rapidly  where  the  conditions  proved 
to  be  most  suitable  ? 

So  it  is  in  many  cases.  The  present  life-conditions 
allow  the  occurrence  of  a  species  whenever  they  have 
no  relation  at  all  to  its  special  characters,  or  whenever 
these  characters  are  fitted  for  them.  If  not,  a  plant 
may  be  accidentally  introduced  and  perhaps  thrive  for 
some  years,  but  in  the  long  run  it  will  always  be  extermi- 
nated. 

The  same  principle  may  be  applied  to  the  origin  of  a  new 
form.  If  its  new  character  is  harmless  or  more  or  less 
suited,  the  type  will  thrive  as  well  as  the  parent  form  from 
which  it  derived  its  origin.  If,  however,  it  proves  to  be 
injurious,  it  goes  without  saying  that  the  form  will  be  con- 
demned to  extermination  after  a  longer  or  shorter  struggle 
for  existence.  Its  only  chance  of  escaping  this  judgment 
lies  in  migration^  by  which,  perhaps,  it  may  find  elsewhere 
more  suitable  Hfe-conditions. 

Returning  to  our  general  discussion  we  may  state  that 
the  study  of  the  relations  of  living  organisms  to  their  present 
environment  must  be  revised  and  rebuilt  upon  quite  new 
principles.  The  quahties  of  the  plants  are  not  the  problem 
to  be  solved.  The  question  is  how  the  given  qualities 
of  the  species  are  suited  to  the  environment,  and  how  they 
enable  the  organism  to  hold  out  against  its  present  enemies, 
and  against  the  dangers  of  chmate  and  winter.  The  question 
has  often  been  discussed  whether  we  are  right  in  speaking 
of  the  use  of  some  character  or  in  saying  that  a  quality 
serves  a  distinct  purpose.  No  doubt,  much  abuse  has  been 
made  of  these  terms,  and  the  common  assumption  that  all 
quahties  must  serve  some  special  purpose  is  evidently 
exaggerated.  The  only  point  which  is  open  for  inquiry  is 
the  question  on  which  marks  of  an  organism  depends  its 
possibiUty  of  hving  and  multiplying  itself  on  the  spot  where 


GEOGRAPHICAL   DISTRIBUTION   OF   PLANTS     345 

we  sec  it,  and  which  other  characters  are  indifferent  in  the 
actual  struggle  for  life. 

In  other  words,  the  principle  of  adaptation,  as  one  of  the 
main  parts  of  the  theory  of  evolution,  should  be  separated 
from  the  study  of  the  geographical  distribution.  Tliis 
latter  science  itself  should  be  divided  into  two  parts,  one 
of  which  would  be  concerned  with  the  dehmitation  of  the 
regions  inhabited  by  organisms  of  various  degrees  of  affinity, 
while  the  second  would  have  to  explain  the  directly  observed 
facts  of  local  occurrence  and  actual  migration.  The  iirst 
of  these  two  parts  is  a  comparative  science  and  is  directly 
related  to  the  theory  of  the  common  origin  of  hving  beings. 
The  second  must  become  an  experimental  inquiry  into  the 
relationship  between  the  quaUtics  of  the  plants  and  those 
of  the  environment,  which  it  may  prefer  or  endure.  All 
speculations  upon  the  relationship  of  organisms  to  special 
features  of  tliis  environment  which  attempt  to  explain 
larger  groups  of  characters  on  the  assumption  of  some 
adaptation,  arc,  to  my  mind,  as  yet  merely  poetical  descrip- 
tions of  the  way  in  which  we  should  Hke  to  understand 
and  admire  nature,  but  not  facts  capable  of  direct  proof. 

Desert  plants  afford  an  instance  which  may  give  a 
clear  appreciation  of  the  two  contrasting  methods  of  explain- 
ing the  nature  of  plants.  AccorcUng  to  the  current  view 
they  are  most  astonishingly  speciahzed  and  adapted  for 
large  regions  where  it  is  impossible  for  other  plants  to 
thrive.  Although  belonging  to  numerous  natural  famiHes, 
and  therefore  showing  hardly  any  genetic  affinity  among 
themselves,  they  enjoy  a  group  of  common  features  which 
show  the  closest  imaginable  relation  to  their  arid  environ- 
ment. Three  main  types  of  desert  plants  may  be  distinguished. 
The  most  common  is  composed  of  the  low  shrubs  with  green 
stems  and  twigs,  a  loose  mode  of  branching,  and  small 
coriaceous  leaves  or,  in  some  instances,  with  no  foliage  at 


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M 

mK 

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1 

Fig.  III.     Palo  \'crde,   or  Parkinsonia  microphylla,   typical  desert  plant 
from  Tucson,  Arizona. 


346 


Fig.  112.     Palo  Christi,  or  Koeberlinia  speciosa,  a  typical  desert  i)lant  from 
Tucson,  Arizona. 


347 


348  PLANT-BREEDING 

all.  All  their  visible  marks  point  to  a  reduction  in  the 
use  of  water,  the  evaporating  surface  being  as  thoroughly 
reduced  as  possible.  Under  the  ground,  the  development 
of  their  root-system  is  ciuite  the  reverse.  The  roots  are 
long  and  widely  branching,  penetrating  to  a  considerable 
depth,  thus  enabhng  the  plants  to  procure  the  necessary 
water. 

The  two  other  types  of  desert  plants  are  the  cacti  and  the 
annual  weeds.  The  roots  of  the  cacti  are  spread  laterally, 
instead  of  growing  to  any  considerable  depth.  They  may 
be  said  to  drain  the  surface  all  around  the  plants.  They  ab- 
sorb the  rainwater  at  the  periods  of  those  short  but  heavy 
showers,  which  for  a  short  time  moisten  the  soil  and  stimu- 
late vegetation.  This  water  is  brought  into  their  fleshy  stems 
and  stored  up,  that  it  may  be  used  afterward  during  the 
long  rainless  seasons.  During  rainy  weather  the  stems 
of  the  cacti  are  seen  to  swell,  shrinking  again  in  the  succeed- 
ing periods  of  drought.  The  annual  weeds  of  the  desert 
are  distinguished  by  the  shortness  of  their  Ufe-time,  this 
being  limited  to  the  few  weeks  of  rainy  weather  in  the 
spring.  As  soon  as  the  summer  begins  and  the  soil 
is  drying,  their  Ufe-cycle  is  completed,  and  only  the  dead 
stems  and  the  numerous  seeds  remind  the  \dsitor  of  the 
profusion  of  flowers  which  have  vanished. 

In  the  mind  of  a  botanist  strolhng  on  the  arid  soils 
amidst  these  most  strange  and  astonishing  forms  of  vegeta- 
tion, the  question  necessarily  arises:  Are  all  these  species 
natives  of  the  desert,  and  have  they  acquired  their  special 
characters  under  the  influence  of  the  long  periods  of  dryness 
and  the  insufiiiciency  of  standing  water  in  the  soil?  Is  it 
the  desert  which  has  made  them  such  as  they  are  now, 
apparently  admirably  suited  for  these  extreme  hfe-conditions  ? 
Or,  on  the  other  hand,  are  they  perhaps  only  a  selected 
few   from   among   the   widely   difl'erentiated   forms,    which 


349 


350  PLANT-BREEDING 

are  everywhere  abundant  in  richer  regions  and  on  more 
favorable  soils?  Are  the  plants  of  the  deserts  only  such 
as  can  endure  the  hardships  of  these  unfavorable  surround- 
ings, all  others  being  stamped  out,  as  soon  as  they  try  to 
transgress  the  hmits  of  these  pecuhar  areas?  Is  not  the 
popular  saying  that  they  are  cast  out,  to  hve  on  the  desert, 
nearer  the  truth  than  the  current  scientific  conception, 
wliich  regards  them  as  the  product  of  their  present  environ- 
ment ? 

To  my  mind  the  answer  to  these  questions  is  given  by 
the  plants  themselves.  This  answer  is:  They  all  prefer 
more  favorable  conditions  to  those  which  are  given  them. 
They  endure  the  desert,  but  only  with  difhculty.  Their  hfe 
is  nearer  starvation  than  enjoyment.  They  are  multiply- 
ing themselves  in  a  procUgious  manner,  not,  however,  from 
luxuriance,  but  on  account  of  the  absence  of  competition. 
They  do  not  thrive,  nor  do  they  unfold  their  full  stature 
and  quahties  as  they  might  under  better  conchtions.  They 
greatly  prefer  irrigated  grounds  or  the  moist  air  of  the 
forest,  and  only  here  display  their  real  nature.  Even 
cacti  are  originally  forest  plants,  and  may  be  seen  stoutlv 
growing  between  densely  thronging  shrubs.  Thus  the 
conviction  is  forced  upon  us,  that  desert-plants  are  not, 
as  a  rule,  the  product  of  aridity.  They  may  have  originated 
anywhere  else,  under  any  other  conditions.  But  through 
their  pecuhar  quahty  of  enduring  drought,  they  attained 
their  rapid  multiphcation  as  soon  as  in  their  migration 
they  reached  the  arid  regions  and  there  found  themselves 
free  from  competition. 

So  it  seems  to  me  in  all  those  beautiful  cases  of  fitness 
for  pecuhar  or  extreme  influences.  \\''e  do  not  know  how 
they  have  been  acquired.  We  may  imagine  that  usefulness 
in  the  struggle  for  hfe  has  preserved  some  quahties,  the 
bearers  of  injurious  characters  being  easily  stam]^ed  out.     We 


►tI 


-"■^ 


3  d 


351 


352  PLANT-BREEDING 

may  sketch  the  development  of  the  spurs  of  the  orchids  in 
connection  with  the  lengtli  of  the  proboscis  of  bees  and 
butterflies,  but  we  cannot  directly  observe  the  changes  which, 
we  assume,  are  brought  about  by  such  influences.  In  all  those 
cases  it  is  equally  possible,  and  in  some  even  probable,  that 
they  have  not  been  originated  in  the  way  in  which  the 
plants  are  now  using  them.  The  higher  the  degree  of 
differentiation,  the  more  probable  our  mode  of  explanation 
may  be,  but  in  the  more  simple  and  ordinary  cases,  includ- 
ing the  desert  plants  and  many  similar  instances,  the  environ- 
ment has  only  selected  the  suitable  forms  from  among  the 
throng,  and  has  no  relation  whatever  to  their  origin. 

Present  distribution  is  the  effect  of  migration,  and 
migration  is  governed  and  directed  by  the  given  characters 
of  the  species.  It  produces  the  intimate  relationship  of  the 
organisms  to  their  environment,  to  climate  and  soil  as  well 
as  to  all  their  vegetable  and  animal  competitors.  But  in 
this  the  qualities  of  the  organisms  are  the  causes,  and  the 
distribution  is  the  effect. 


INDEX. 


"Abundance"    plum,    21 1. 

Achillea  atrafa,  342,  343  fig.;  mos- 
cliata,   342,   343  fig. 

Adaptation,  345. 

Advertisement  of  pedigree  wheat, 
40   fig. 

Agricultural  breeding.  Discovery 
of  Nilsson  and,   93. 

Agricultural  experiment  station  at 
Svalof,  48  ff.,  272;  of  Kansas, 
125  fig.°;   of  Minnesota,    103.  fig. 

Agricultural  plants.  Discovery  of 
elementary  species  of,   29. 

Agrostis,    170. 

Alhambra   plum,    213. 

Amaryllis,    162;    hybrids,   207. 

Amelioration,  German  methods  of 
selection  and,  56;  Gradual,  31; 
of  agricultural  plants  by  selec- 
tion. Explanation  of,  99;  of  ap- 
ples  and  pears,   256. 

Amsterdam,  Experiment  garden  at, 
IS  fig.,    143  fig.,  323   fig. 

Analysis  of  varieties  of  cereals,  68. 

Anthocyanin,   246,   248. 

Anthoxanthum,    170. 

Apples,     Amelioration     of,     256; 
Seedless,    188,   257. 

Apricot  and  plum  hybrids,  218. 

Asclepias,    170. 

Atropa  Belladonna,   243   fig. 

Australian  star  -  flower,  169  fig., 
172;  Improved  everlasting,  171 
fig. 

A\ena  elatior,  285  fig. ;  Flower  of, 
278  fig.;   Forms  of,  286. 

Azolla  carolinensis,   334. 


Barley,  breeding  for  stiff  culms, 
63;  Constancy  of,  89;  Hallett's 
Chevalier,  39  fig.,  44,  269;  Meal- 
iness of,  287:  Prentice,  65;  Pri- 
mus, 240,  269;  Princess,  65; 
selection  for  strong  straw,  239; 
Spikelet  and  flowers  of,  279  fig. ; 
Transparency   of,    287. 

Barrenness  in  corn,    141,    145  fig. 

Bartlett  plum,   226. 

Bateson  on  discontinuous  evolu- 
tion,  8. 

Beach  plum,   212. 

Beans,    Windsor,   248. 

Beech,    Seedling-plants   of,    295  fig. 

Beets,  Amount  of  sugar  in.  304; 
Methodical  study  of,  284;  Se- 
lection in  sugar-,  94;  Sugar-, 
307- 

Belladonna,   243,   244. 

'"Bellevue  de  Talavera"  wheat,  32 
fig-,  33- 

Berries  and   flowers,   244. 

Blackberry,    \Miite,    189. 

Bore-wheat,    Svalof,    267  fig. 

Brambles,    185;    Laciniate,    249  fig. 

Breeding,  Agricultural,  93 ;  blocks 
of  corn,  155  fig.;  by  isolation  of 
individuals,  67;  corn,  107  ff.; 
corn  for  oil,  108  fig. ;  Correla- 
tions in  agricultural,  255  ff . ; 
English  vs.  German  method,  65; 
German  method  of,  46;  Meth- 
ods of  corn,  133;  of  cereals,  29 
ff. ;  of  corn,  History  of,  130; 
plots,    137. 

Brodisa,    170. 


354 


PLANT-BREEDING 


Bud  sports,   232. 

Bulbs   of   hyacinths,    247. 

Burbank  (Luther),  De  N'ries  and 
Shull,  165  fig.;  Experimental 
garden  of,  163  fig. ;  Farm  of,  at 
Santa  Rosa,  Cal.,  161  fig. ;  Por- 
trait of,  1 58  fig. ;  Production  of 
horticultural  novelties  by,  159 
ff. ;   Methods  of,   159. 

Burbank  canna,  200;  giant  prune, 
179  fig.;  plum,  170,  211;  Shasta 
daisies,  195  fig. ;  sugar  prune, 
181  fig. 

Butt   summer  wheat,   75  fig. 


Cactus,  Giant,  349  fig. ;  hybrid,  193 
fig.;  Spineless,  168,  192;  Spine- 
less edible,  193  fig.,  226,  227  fig., 
228,   229  fig. 

Calla  sethiopica,  204;  albo-macii- 
lata,  207;  Elliottiana,  206;  "Fra- 
grance," 204;  Fragrant,  224; 
hastata,  206;  Nelsoni,  206,  232; 
Pentlandi,  206;  Rehmannii,  232; 
Tiny,  compared  with  normal 
size,   205  fig. 

Campion,    Smooth-leaved,    341  fig. 

Cannas,  Burbank,  flaccida,  flower- 
ing, and  Tarrytown,  200. 

Capsules  and  general  development, 
Correlation   of,    307. 

Carnegie   grant,    162. 

Celandine,   251  fig. 

Centaurea    Melitensis,    334. 

Cephalipterum    Drummondii,    172. 

Cereals,  Breeding  of,  29  fi';  Corn 
differs  from  other,  120;  Ele- 
mentary species  among,  105;  Or- 
igin of  variability  of,  84;  Sports 
of,  at  Svalof,  85;  Svalof  breed- 
ing of,    48. 

Cereus   giganteus,    349  fig. 

Chamomile,   Wild,  334. 

Chance  seedlings,   222. 

Characters  and  environment,  335; 
in  nature.  Association  of.  237; 
Parallelism  of  apparently  inde- 
pendent, 296;  Unit-,  16,  242, 
309. 

Chelidonium  majus,   251  fig. 


Cherry,  Mahaleb,  223;  and  plum 
hybrids,   218. 

Chestnut,    Spineless,    234. 

Chevalier    barley,    39  fig.,    44,    269. 

Chrysanthemum  scgetum,  11,  13 
fig-.  235. 

Classificators,    287. 

Clematis    hybrid,    209. 

Close  pollination  of  corn,   122. 

Clovers,  Correlations  in,  258; 
Hastening  of  germination  of, 
262;  Pitchers  of,  293  fig.; 
Types   of,    282. 

Collections  of  selected  plants,  288. 

Color,  and  form,  Correlations  be- 
tween, 250;  and  taste.  Correla- 
tions between,  248;  of  hybrids 
of  N'eronica  longifolia,  247;  of 
thorn-apples,  246;  -varieties  and 
seeds,    244. 

Columbine,  Flowers  of,  241  fig.; 
hybrid,   209. 

Concordea  pea,   Svalof,    69  fig. 

Constancy  of  elementary  species, 
100;  of  minor  variations,  118; 
of  species,   8. 

Cope    on  discontinuous  evolution,  8. 

Corn,  Barrenness  in,  141,  145  fig. ; 
breeding,  107  ff. ;  Breeding 
blocks  of,  155  fig.;  breeding. 
History  of,  130;  breeding.  Meth- 
ods of,  133;  Comparative  trial 
of  progeny  of,  137;  Cross-polli- 
nation of  sweet,  123  fig.;  Dent, 
114;  Detasseling  of,  140;  differs 
from  other  cereals,  120;  Equal- 
ity of  kernels  in,  147;  Flint, 
114;  for  oil.  Breeding,  108  fig.; 
hybridizing,  125  fig.;  Individual 
rows  of,  135  fig. ;  Inflorescence 
of,  121  fig.;  Kernel  of,  153  fig.; 
Methods  of  testing,  137;  mon- 
strosities, 113  fig.,  1 15  fig.,  117; 
Pistillate  flowers  of,  ii9fig. ; 
Pod,  114;  Pollen  of,  122;  Polli- 
nation of,  122;  Pollination  of, 
by  hand,  126,  129  fig.;  Pop,  114; 
Ramified  cob  of,  115  fig. ;  Selec- 
tion in,  134,  148;  Soft,  116; 
.Staminate    spikelet    of,     119  fig.; 


INDEX 


355 


Sweet,  ii6,  149  fig. ;  Types  of, 
III  fig.,  114;   yield  per  acre,  i  10. 

Correlation,  18,  J44,  258;  between 
color  and  form,  250;  between 
color  and  taste,  248;  Factors  of, 
304;  in  agricultural  breeding, 
255  ff.;  in  fluctuating  variabil- 
ity, 289  ff. ;  in  panicles  of  oats, 
265;  Methodical  study  of,  271 
ff. ;  of  capsules  and  general  de- 
velopment, 307 ;  within  the  flow- 
ers, 250. 

Corylus  Avellana   laciniata,    7  fig. 

Cross-pollination  of  corn,  122;  of 
sweet  corn,    123  fig. 

Crosses,  316;  Accidental,  80;  not 
always   successful,    219. 

Crossing,  New  characters  not  pro- 
duced bj',  187;  New  varieties 
bv,    174. 

Culture,  Pedigree,  42;  Pedigree, 
of  Lamarck's  evening  primrose, 
20. 

Currant,  California,  184;  Color  in 
flowering,  247;  Gordon's,  314 
fig.,  316;  Hybrid  of,  316;  Flow- 
ering, 315  fig.;  Yellow,  315  fig- 
Dahlia,   Fragrant,   224. 

Daisies,  Burbank's  Shasta,  195  fig.; 
Shasta,   196,    198  fig. 

Danebrog   opium   poppy,    319  fig. 

Darwin,  Natural  Selection  discov- 
ered by,  91;  on  origin  of  spe- 
cies by  sports,  6 ;  theory  of  des- 
cent,  I,  90. 

Datura  Stramonium,  Color    of.  246. 

Datura  Tatula,   Color  of,   246. 

Descent,  Darwin  theory  of,  i,  90; 
Lamarck   theory   of,    i,    90. 

Desert  botanical  laboratory  at  Tuc- 
son, Arizona,  351  fig.;  jilants, 
345- 

Detasseling  of  corn,    140. 

De  Vries,  Burbank  and  ShuU,  165 
fig. 

Dewberry,    Californian,    186,    187. 

Dipsacus   sylvestris,    Twisted  stems 

of,  144  fig- 
Distribution,  and  migration,  352; 
Geographical,    of    plants,    333  ff. 


Dollo    on    discontinuous    evolution, 

8. 
Dracocephalum  moldavicum,    ii. 
Drechsler,  breeder  of  cereals,   46. 

Elseagnus,    185. 

Elodea  canadensis,  334. 

Elofson,   Work  of,   277. 

Environment    and   characters,    335. 

Epigeia   repens,    225. 

Epilobium  hirsutum,  Elementary 
forms  in,   100. 

Equisetum     Telmateja,     Twisted 
stems  of,    144  fig. 

Eryobothrya  japonica,    183. 

Ei^chscholtzia  californica,   234. 

Everlasting,    172. 

Evolution,  and  mutation,  i  ff. ;  Dis- 
continuous, 8;  Nilsson  on  slow, 
14:  Theory  of,  i;  Time  re- 
quired  for   slow,   4. 

Fasciations,    144,   293. 
Fertilization  of  corn,    122,    151;   of 

evening   primroses,    252. 
Figwort,     Seedling-plants     of,     295 

fig- 
Flag-oats,    Svalof,    76  fig. 
Flax,   Correlations  in,   258. 
Flowers,     Berries     and,     244;      of 

corn,  119  fig.;    Varieties  of  fruits 

and,    178. 
Fluctuation,    5. 

Fouquieria   splendens,    351  fig. 
Frit-fly,    264. 
I'ruits    and    flowers,    \'arieties    of, 

1 78. 
Fruwirth,   Work  of,   294. 
Funk    Brothers    Seed    Company, 

breeders  of  corn,    132. 

Garden,  Experiment,  at  Amster- 
dam, 15  fig-;  143  fig-:  3^3  fig-: 
of  Luther   Burbank,    163  fig. 

Geographical  distribution  of  plants 
333  f(- 

Germination  and  size  of  seeds, 
261:  of  clover,  Hastening  of, 
262. 

Golden    Drop  Wheat.   44. 

Grading    selected    plants,    288. 


356 


PLANT-BREEDING 


Grape,   Pierce's,   232. 

Grasses,      170;     Methodical     study 

of   meadow-,    284. 
Gregory,  J.  J.  H.,   and  Son,    162. 
Grenadier   wheat,    Svalof,    266  fig. 
Crop  pea,   Svalof,   283  fig. 
Gwallig,   Work  of,  294. 


Hallctt,   E.    F.,   breeder  of  cereals, 

38. 

Hallett's  advertisement  of  pedi- 
gree wheat,  40  fig.;  Chevalier 
barley,  39  fig. ;  "Original  Red 
Wheat,"   41;   wheat,  39  fig. 

Hand  pollination  of  corn,    126,  129 

fig- 
Hays,    W.    M.,    breeder    of    wheat, 

45;   Work  of,    loi. 
Hazelnut,  Oak-leaved,   7  fig. 
Heine,   breeder  of  cereals,   46. 
Heuchera,     Hybrid,     197,     201  fig.; 

micrantha   and   sanguinea,    199 
History  of  corn  breeding,    130. 
Holden,     P.  G.,    breeder    of    corn, 

132- 

Hopetown  oats.   35;   wheat,   35. 

Hopkins,  Cyril  G.,  breeding  corn 
from  single  ears,  131;  Discov- 
eries of,   154. 

Hops,   Correlations  in,  258. 

Hordeum  erectum,   269. 

Horsetail,  Twisted  stems  of,  144 
fig. 

Horticultural  novelties  by  Luther 
Burbank,    Production    of,     159  ff. 

Horticulture,   Mutations   in,   221  ff. 

Hunneniannia    fumariaefolia,    170. 

Hunter's  wheat,   41. 

Hyacinths,   Bulbs  of,   247. 

Hybrid  amaryllis,  207 ;  apricot,  218; 
cactus,  193  fig.;  cactus  seedlings, 
191  fig.;  cherry,  218;  clematis, 
columbine,  California  poppy, 209; 
Heuchera,  197,  201  fig.;  currant, 
314  fig. ;  plums,  210,  218;  pop- 
pies, 232,  233  fig.;  poppies. 
Leaves  of,  231  fig.;  Tobacco  and 
petunia,  219;  \'eronica  longifo- 
lia,  247;  walnut,  173  fig.,  174, 
1/5  fig-    177  fig- 


Hybrids,  72,  313;  Splitting  of,  80; 
Unit-characters  in,    16. 

Hybridization,  a  means  of  increas- 
ing variability,  186;  and  selec- 
tion,  202. 

Hybridizing  corn,    125  fig. 

Inflorescence   of   corn,    121  fig. 
Isolation   of   individuals,    Breeding 
by,  67. 

Kansas    agricultural    experiment 
station,    125  fig. 

Kclsey   plum,    213. 

Kernel   of  corn,    1 53  fig. 

Kiebcrlinia  speciosa,  347  fig. 

Korshinsky  on  discontinuous  evo- 
lution,  8. 

Laboratory    at   Tucson,    Arizona, 
Desert  botanical,  351  fig. 

Lamarck  theory  of  descent,    i,  90. 

Lathyrus  heterophyllus,  pratensis, 
and  sylvestris,  284. 

Learning,  J.  L.,  breeder  of  corn, 
130. 

Leaves,    Pitcher-like,   292. 

Le  Couteur,  breeder  of  cereals,  33. 

Leguminous  plants.  Elementary 
types  of,   284. 

Leland  Stanford  Junior  Univer- 
sity,   162. 

Lilacs,    Double-flowered,     188. 

Lilium  pardalinum,  208. 

Lime  tree.    Pitchers  of,   293  fig. 

Linaria  vulgaris  peloria,    11,   12  fig. 

Lochow,  Petkus  von,  breeder  of 
rye.   45. 

Lolium,   170. 

Loquat,   183. 

Lotus  uliginosus,   284. 

Lundberg,  Work  of,  277. 

Lupinus  angustifolius.  Seeds  of, 
244. 

Lupins.    Seeds  of,    244. 

Lychnis   Preslii,    341,    342. 

Magnolia,    Pitchers   of,    293  fig. 
Marguerites,    European,    199. 
Marigold,     Double,     235;       Double 
corn-,    II,    13  fig.,   303  fig- 


INDEX 


357 


Matricaria   chamomilla,   334. 

Matthiola    incana,     Selection    of 
double,    238. 

Maynard  plum,    211. 

Meadow-grasses,  JNIethodical  study 
of,   284. 

Methods  of  breeding,  English  vs. 
German,  65;  German,  46;  of 
Burbank,  159;  of  corn-breeding, 
133!  of  producing  improved  ra- 
ces, Svalof ,  67 ;  of  selection  and 
amelioration,  German,  56;  of 
selection  developed  by  Nilsson, 
Summary  of,  90:  of  testing  and 
comparing,  61;  of  testing  corn, 
137- 

Migration,  335,  345;  and  distribu- 
tion, 352. 

Minnesota,  Agricultural  experi- 
ment  station   of,    103  fig. 

Mokry,   breeder  of  cereals,   46. 

Monstrosities,  142,  144,  292;  of 
corn,    113  fig.,    115  fig.,    117. 

Mungoswell's  wheat,  35. 

Mutability,   6,    100. 

Mutation,  6;  and  evolution,  i  ff. ; 
at  Svalof,  85:  in  horticulture, 
221  ff. ;  of  evening  primroses, 
322. 

Nicotiana,  170;  aflRnis,  209;  glauca, 
209. 

Nightshade,    Deadly.    243  fig. 

Nilsson,  Hjalmar,  and  agricultural 
breeding.  Discovery  of,  93;  Dis- 
covery of  elementary  species  of 
agricultural  plants  by,  29;  por- 
trait, 28;  method  of  selection. 
Summary  of,  90;  methods,  104; 
on  slow  evolution,  14;  Work  of 
277- 

Nilsson-Ehle,    \\"ork    of,    277. 

Oat  -  grass,  Spikelet  of,  278  fig. ; 
Wild,   285  fig. 

Oats,  Correlation  in  panicles  of, 
265;  Hopetown,  35;  Panicles  of, 
263  fig. ;  Races  of,  36;  Shirreff, 
35:  sports  at  Svalof,  89;  Stiff- 
branched  Svalof,  82  fig. ;  Svalof 
flag-,    76    figure;     with    bending 


branches,  Svalof,  86  fig.;  with 
spreading  branches,  Svalof,  83 
fig.;  with  stiff  branches.  Panicle 
of,  275  fig. ;  with  weak  branches. 
Panicle  of,  273  fig. ;  with  weak 
branches,    Svalof,   87  fig. 

Qinothera  albicaulis,  170;  biennis, 
253,  250,  338;  biennis.  Elemen- 
tary forms  in,  100;  biennis  X 
muricata,  318;  brevistylis,  325 
figure;  brevistylis,  plementary 
forms  in,  100;  brevistylis.  Mu- 
tative origin  of,  322:  gigas,  22, 
23  fig-,  328,  329  fig.;  Hookeri, 
336;  Lamarckiana,  17  ff.,  324, 
329  fig. ;  laevifolia,  331  fig.;  lae- 
vi  folia.  Elementary  forms  in, 
100;  lata,  20,  326;  leptocarpa, 
22:  muricata,  337  fig.,  338;  na- 
nella,  21  fig.,  22;  oblonga,  24, 
328;  rubrinervis,  21  fig., 125  fig., 
328;  scintillans,  19  fig.,  328; 
scintillans.    Rosette  of,    330  fig. 

Oil,  Breeding  corn  for,  108  fig.; 
Selection   for,    154. 

Opuntia  Engelmanni,  32S;  vulga- 
ris,  228. 

Oscinis  frit,    264. 

Palo    Christi.    347  fig. ;    \'erde,  346. 

Pansy,    31 1  fig. 

Papaver    orientale,     209;     pilosum, 

233  fig. ;    Rhoeas,    209,   234;    som- 

niferum,    209;    somniferum,    Pis- 

tillodous,    297. 
Parallelism     of     apparently     inde- 
pendent  characters,   296. 
Parkinsonia    microphylla,    346  fig. 
Pea,     Svalof     Concordia,     69   fig.; 

Svalof    Grop,    283   fig.;       Svalof 

Solo,    281  fig. 
Peas,     Kinds    of,     280;     sports    at 

Svalof,     89;     Tedin's     work     on, 

255- 
Pearl    summer    wheat,     Svalof,    74 

fig- 
Pears,    Amelioration   of,    256. 
Pedigree,   cultures,  42;    cultures  of 

Lamarck's  evening  primrose,  20; 

of  spineless  cactus,    168. 
Peloria,   293. 


358 


PLANT-BREEDING 


Petkus,    Rye  of,   46. 

Petunia,  Hybrid  between  tobacco 
and,   219. 

Pierce's  grape,   232. 

Pisum    arvense    and    sativum.    255. 

Pitchers,    292. 

Plots,    Breeding,    137. 

Plum,  215  fig.:  and  apricot  hy- 
brids, 218;  and  cherry  hybrids, 
218;  Bartlett,  226;  Burbank, 
170;  Hybrid,  210;  Satsuma,  170; 
Sorts   of,    211  f(.:   W'ickson.    175. 

P!u meets,   218. 

Pollen  of  corn,   122. 

Pollination,  220;  of  corn,  122;  of 
corn  by  hand,  126,  129  fig.;  of 
evening  primroses,  252  f . ;  of 
svi'eet   corn,    Cross-,    123  fig. 

Poppy,  Blue,  234;  Californian, 
209;  Common,  209;  Danebrog 
opium,  319  fig.;  Hybrid,  232, 
233  fig.;  Leaves  of  hybrid,  231 
fig.;  Opium,  209;  Pistillodous 
opium-,  297;  Polycephalous  opi- 
um, 299  fig. ;  Scarlet  California, 
234;  Seedling-plants  of,  295  fig. ; 
Seeds  of  opium,  244;  Young 
opium,   301  fig. 

Potatoes,  Correlations  in,  258: 
Methodical  study  of,  284. 

Prentice  barley,  65. 

Primrose,  Evening,  170,  250:  Flow- 
ers of  Evening-,  252  fig. ;  Fruits 
of  Evening-,  305  fig. ;  Hybrid  of, 
318;  Lamarck's  evening-,  17  ff., 
327  fig.  ;Mutations  of  evening-, 
322;  Rosette  of  Lamarck's  even- 
ing-. 330  fig. ;  Seedling-plants  of 
Evening-,  295  fig. ;  Short-styled 
evening-,  325  fig;  Smooth-leaved 
variety   of  the  evening-,   331  fig. 

Primus-barley,    240,    269;    berry, 
186. 

Princess  barley,   65. 

Pringle's  wheat,   36. 

Progeny,  Mixed,  73 ;  of  corn.  Com- 
parative trial  of,  137;  Uniform, 
72. 

Protein,    .Selection   for,    154. 

Prune,  Burbank  giant,  179  fig.; 
Burbank     sugar,     181  fig. ;     Cali- 


fornia sugar,  172;  Stoneless, 
189,  190  fig.,  226. 
Piunus  Americana  X  nigra,  213; 
Mahaleb,  223;  maritima,  212: 
Pissardi,  213,  215  fig.;  Simoni, 
213,   226;   triflora,    176,   213. 

Quetelet's  law  of  variability,   5. 
Quince,    Japanese,     183;     Selection 
of,  239. 

Races,  Pure,  77;  Self-dependent, 
95;  Types  of,  94. 

Raspberry,  Cuthbert,  187;  Sibe- 
rian,   186. 

Records,   N'alue  of  scientific,   71. 

Rhodanthe,    170. 

Rhubarb,    Crimson,    172. 

Ribes.  aureum,  315  fig.;  Gordon- 
ianum,  314  fig.,  316;  sanguin- 
eum,  :84,  247,  315  fig.,  316; 
sanguineum  glutinosum,  185; 
sanguineum  X  aureum,     316. 

Richardia   africana,    204. 

Riley,  James,  breeder  of  corn,  131. 

Rimpau,   breeder   of   cereals,    46. 

Rimpau's  rye  of  Schlanstedt,  95, 
97  fig- 

Kubus  Californicus,  186;  fruti- 
cosus  laciniatus,  249  fig.;  Sibi- 
ricus,    186. 

Rye  of  Petkus,  46;  of  Schlan- 
stedt,  46,   95,   97  fig. 

Satsuma  plum,   170,  211. 

Schindler,   Work  of,   294. 

Schizanthus,    170. 

Schlanstedt,  Rimpau's  rye  of,  95, 
97  fig. ;   Rye  of,   46. 

Schribaux  on   Schlanstedt  rye,    96. 

Scott  on  constancy  of  species,  8. 

.Scrophularia     nodosa.     Seedling 
plants    of,    295  fig. 

Seed-grain  society  for  Sweden,   54. 

.Seedlings,  295  fig. ;  Chance,  222; 
Hybrid  cactus,  191  fig.;  Seeds 
and  color-varieties,  244;  Size 
and  germination  of,  261;  Size 
and   integuments  of,   259. 

Selection,  and  amelioration,  Ger- 
man method  of,  56;  Causes  of 
improvement     in     repeated,     66; 


INDEX 


359 


developed  by  Nilsson,  Summary 
of  method,  90;  discovered  by 
Darwin,  Natural,  91;  Explana- 
tion of  amelioration  of  agri- 
cultural plants  by,  99;  for  oil 
and  protein,  154:  for  strong 
straw,  Barley,  239;  is  intra-spe- 
cific,  94;  of  corn,  134;  of  double 
common  stock,  238;  of  quinces, 
239;  of  samples,  70;  Hybridiza- 
tion and,  202;  of  individuals, 
/i;  in  sugar-beets,  94;  Natural, 
and  mutation,  9;  Principle  of 
continuous,  90  ff. ;  Principle  of 
natural,  2;  Repeated,  150,  2^2: 
Sufficiency  of  initial,    73. 

Selections,    Burbank's,    on    large 
scale,    167. 

Shasta  daisies.  196,  198  fig. ;  Bur- 
bank's,    195  fig. 

Shirreflf,  Patrick,  breeder  of  cer- 
eals,   34. 

Shirreff's  bearded  red  wheat.  36; 
bearded    white    wheat,    36:    oats. 

35- 
Shull,   Burbank  and  De  \'ries.    165 

fig. 

Silene      odontipetala.       Seedling 
plants    of,    295  fig. 

Slow  evolution,    Nilsson   on.    14: 
Time  required   for,    4. 

Snapdragon    and    its    color    varie- 
ties,  3 1 7  fig- 
Society     for     Sweden,     .Seed-grain, 
54- 

Solo  pea,    Svalof,    281  fig. 

Species  among  cereals,  Elemen- 
tary, 105;  Constancy  of  elemen- 
tary, 100;  Elementary,  of  agri- 
cultural plants,  29;  Origin  of, 
92;  Origin  of  elementary.  81; 
Origin  of,  by  mutations,  9,  26; 
Scott  on  constancy  of,  8. 

Splittings  in   hybrids,   316. 

Sports,  223;  at  Svalof,  89:  at 
Svalof,     Cereal,     85. 

Spurs,    Cause    of,    241. 

Star  -  flower,  Australian,  169  fig., 
172;  Improved  everlasting  Aus- 
tralian,   171  fig. 

Staliotes  aloides,  338. 


Stipa,    170. 

Stock,   Common,   238. 

Stocks,   Seeds  of,  244. 

Svalof,  Agricultural  experiment 
station  at,  48  ff.,  272;  breeding 
of  cereals,  48;  Bore-wheat,  267 
fig. ;  Concordia  pea,  69  fig. ;  flag- 
oats,  76  fig.;  Grenadier  wheat, 
266  fig. ;  Grop  pea,  283  fig. ; 
method  of  producing  improved 
races,  67;  oats,  Stiff-branched, 
82  figure;  oats  with  bending 
branches,  86  figure;  oats  with 
spreading  branches,  83  fig. ;  oats 
with  weak  branches,  87  figure; 
Pearl  summer  wheat,  74  fig. ; 
Solo  pea,    281  fig.;   village,    50. 

Sweden;  Seed-grain    society  for,  54. 

"Sweet    Brotan"    plum,    211. 

Syringa  azurea  plena,    188. 

Tannin,    248. 

Tarrytown  canna,   200. 

Taste,  Correlations  between  color 
and,  248. 

Teasels,    Torsions    among,     142; 
Twisted   stems   of,    144  fig. 

Tedin's  work  on  peas,   255. 

Testing   corn,    Methods   of,    137. 

Tliistle,   Napa-,   334. 

Tliorn-apples.    Color   of,    246. 

Toadflax,   Peloric,    11,    12  fig. 

Tobacco,  and  petunia.  Hybrid  be- 
tween, 219;  Fragrant,  170,  209; 
Pitcher-like  leaf  of,   291  fig. 

Torsions   among  teasels,    142. 

Tiifolium  incarnatum,   261. 

Triticum  polonicum,   30  fig. 

Unit-cliaracters,    16,   242,   309. 
Units.   310. 

\'ariability,  3;  Constancy  of  mi- 
nor, 118;  Correlations  in  fluctu- 
ating, 289  ff.;  Correlative,  332; 
I'luctuating,  5,  100,  183;  Hy- 
bridization a  means  of  increas- 
ing, 186;  Kinds  of,  182;  of  the 
cereals.  Origin  of,  84;  of  corn 
within  the  varieties,  118;  of  ray- 
florets.     Fluctuating,     306;     Pro- 


36o 


PLANT-BREEDING 


duction     and     augmentation     of, 
182 ;   Range  of,    183. 

X'arieties,  Agricultural,  84:  by 
crossing,  174;  comparative  stud- 
ies, 79;  Horticultural,  84;  of 
cereals.  Analysis  of,  68;  of 
fruits  and  flowers,  178;  Testing 
new,  78;  Variability  of  corn 
within    the,    118. 

\'erbena.    Fragrant,    224. 

Veronica    longifolia,    245  fig.,    247. 

Vetch,  Correlations  in,  258;  Seeds 
of  white,   244. 

Vetches    sports    at    Svalof,    89; 
Types  of,  282. 

Vicia  Cracca,   and  Faba,   248. 

Victoria  wheat,  41. 

\'iola  lutea  grandiflora,  311  fig.; 
tricolor,  31 1  fig. 

Wallden,    Work   of,    2-7. 
Walnut,  Hybrid,    173  fig.,    174,    175 
fig.,    177  fig.;   Sweet,   325. 


Wheat,  Butt  summer,  75  figure; 
Golden  Drop,  44;  Hallett's.  39 
fig.;  Hallett's  advertisement  of 
pedigree,  40  fig. ;  Hallett's  orig- 
inal red,  41;  Hopetown,  35; 
Hunter's  41;  Mungoswell's,  35; 
Poland,  30  fig.;  Pringle's  36; 
Races  of,  32  fig.;  Shirreff's 
bearded  red,  36;  Shirreff's 
bearded  white,  36;  sports  at 
Sval6f,  86;  Svalof  Bore-,  267 
fig.;  Svalof  Grenadier,  266  fig. ; 
Svalof  Pearl  summer,  74  fig. ; 
\'ictoria,    41. 

Wickson  plum,    175. 

Wind-pollination   of   corn,  122,  124. 

Witt,   Work  of,  277. 

Wulfenia    carinthiaca,  339  fig.,  340. 

Zea  Mays  amylacea,  116;  inden- 
tata,  114;  saccharata,  116,  tuni- 
cata,    114. 


UtOnRTY  UBSARf 
v.  C.  StaU  CaUefC 


Open  Court  Biological  Series 

HUGO  DE  VRIES 

Species  and  Varieties,  Their  Origin  by  Mutation,  Lectures 
delivered  at  the  University  of  California  by  Hugo 
de  Vries,  Professor  of  Botany  in  the  University  of 
Amsterdam.  Second  thoroughly  revised  and  cor- 
rected edition,  with  portrait  in  photogravure.  1906. 
Pages   xviii,   847.     Price  $5.00  net.      (21s.net.) 

It  is  evident  that  the  new  theory  of  mutations  must  be  recog- 
nized in  all  discussions  of  questions  as  to  origin  and  develop- 
ment. For  instance,  if  the  empirical  view  of  consciousness  be 
taken,  why  should  it  not  be  quite  possible  that  this  has 
appeared  in  the  phylogenetic  development  of  certain  species 
as  a  mutation  ?  And  what  becomes  of  those  arguments  for 
design  which  have  been  based  on  adaptation  by  slow  accumu- 
lative changes  ?  Evidently  the  work  of  De  Vries  may  well 
prove  to  be  an  epoch  making  contribution  to  the  advance  of 
knowledge.  It  makes  the  study  of  evolution  in  part  experi- 
mental, modifies  the  current  views  as  to  origin,  selection  and 
adaptation,  and  finds  a  place  for  non-heredity  and  discon- 
tinuity, for  chance  and  irregularity. — Edward  G.  Spaulding 
in  The  Philosophical  Revieiv. 

EDWARD  DRINKER  COPE 

Among  American  naturalists  Cope  takes  decidedly  a  most 
prominent  rank.  His  numerous  original  contributions 
to  paleontology,  and  observations  in  other  lines  have 
been  largely  accepted  by  his  colleagues,  while  his  in- 
terpretation of  the  doctrine  of  evolution,  has  been  a 
powerful  factor  in  the  formation  of  modern  thought. 

The  Primary  Factors  of  Organic  Evolution,  by  the  late  E.  D. 
Cope,  Ph.  D.,  Member  of  the  United  States  National 
Academy  of  Sciences:  Professor  of  Zoology  and  Com- 
parative Anatomy  in  the  University  of  Pennsylvania. 
Second  edition.  1904.  121  illustrations.  Pp.  550. 
Tables,  bibliography  and  index.  Cloth  $2.00  net. 
(10s.) 

"Will  stand  as  the  most  concise  and  complete  exposition  of 
the  doctrines  of  the  Neo-Lamarckian  school  hitherto  published. 
A  most  valuable  text-book  for  teachers  and  students." — 
Science,  N.  Y. 

"A  work  of  unusual  originality.  No  one  can  read  the  book 
without  admiring  the  intimate  knowledge  of  facts  and  the 
great  power  of  generalization  w^hich  it  discloses." — Prof.  J. 
McK.  Cattell. 

"A  thoughtful  and  scholarly  presentation  unencumbered 
by  guesses  at  facts  or  reasoning  from  probabilities." — Ameri- 
can Register,  Paris. 


2  OPEN  COURT  BIOLOGICAL  SERIES. 

TH.  EIMER 

Professor  Eimer  was  the  teacher  of  Professor  Weismann 
at  Tuebingen.  He  has  written  voluminous  works  and 
his  system  has  received  much  attention  in  Germany. 
His  theory  is  based  mainly  on  the  observation  of 
butterflies,  while  his  famous  disciple,  Weismann, 
relies  chiefly  on  the  generalization  of  facts  derived 
from  the  observation  of  ants.  Although  they  re- 
mained personal  friends,  they  dift'er  in  their  con- 
clusions. 

The  pamphlet  On  Orthogenesis  (i.  e.,  evolution  in  a  defi- 
nitely determined  direction)  is  a  condensed  statement 
of  his  theory  made  by  the  professor's  own  hand,  and 
it  acquires  an  additional  zest  by  being  a  tilt  at  arms 
directed  against  Weismann's  Germinal  Selection.  (See 
page  4.) 

On  Orthogenesis  (Definite  Evolution)  or  the  Impotence  of 
Darwinian  Selection  in  the  Formation  of  Species.  By 
Th.  Eimer,  Professor  of  Zoology  in  the  University  of 
Tuebingen.  Translated  bv  Thomas  J.  McCormack. 
19  cuts.     Pp.56.     Paper  25c.      (Is.  6d.) 

This  little  brochure  was  written  in  reply  to  Weismann's 
"Germinal  Selection."  Prof.  Eimer  is  a  Neo-Lamarckian, 
and  his  special  doctrine  of  orthogenesis  is  declared  to  be  a 
universally  valid  law,  framed  to  show  that  organisms  develop 
in  definite  directions,  without  regard  for  utility,  through  purely 
physiological  causes,  through  the  transmission  of  acquired 
characters,  through  the  combined  agency  of  the  constitution  of 
the  animal  and  the  effects  of  outward  influences. 

CARL   VON  NAEGELI 

Naegeli  was  the  first  to  propose  the  general  theory  of  cell- 
formation  as  accepted  today.  His  little  brochure  on 
"A  Mechanico-Physiological  Theory  of  Organic  Evo- 
lution "  is  a  synopsis  of  his  great  work  on  evolution 
and  will  render  his  diiificult  theories  accessible  to 
English-speaking  students,  to  whom  they  have  been 
hitherto  almost  a  sealed  book. 

A    Mechanico-Physiological    Theory    of    Organic    Evolution. 

Summary.  By  Carl  von  Xaegeli.  Translated  by  V.  A. 
Clark  and  F.  A.  Waugh,  of  the  University  of  Vermont. 
The  only  original  account  of  Naegeli's  theories  in 
English.      Pp.,  52.     Price,  paper,  15  cents.     (9d.) 


OPEN  COURT  BIOLOGICAL  SERIES.  3 

FERDINAND  HUEPPE 

Professor  Hueppe  has  been  the  leading  authority  in  bac- 
teriological lines  and  he  could  find  no  better  inter- 
preter to  make  his  book  accessible  to  English  readers 
than  Dr.  Edwin  O.  Jordan,  Head  Professor  of  Bacteri- 
ology in  the  University  of  Chicago. 
The  Principles  of  Bacteriology.  By  Dr.  Ferdinand  Hueppe, 
Professor  of  Hygiene  in  the  University  of  Prague. 
Translated  from  the  German  and  annotated  by  Edwin 
O.  Jordan,  Ph.  D.,  Professor  in  the  University  of 
Chicago.  28  cuts.  Five  colored  plates.  Pages,  465 — x. 
Price,  $1.75  net  (9s).  Invaluable  to  the  physician, 
the  scientist,  the  student  of  hygiene,  and  practical 
people  in  all  walks  of  life.  ■ 

"In  place  of  a  mere  repetition  of  methods  and  enumeration 
of  species,  Professor  Hueppe  has  grappled  with  the  fundamental 
questions  concerned,  and  has  in  clear  language  given  a  cogent, 
philosophical  and  scientific  account  of  bacteria  and  their  rela- 
tions to  the  processes  with  which  they  are  said  to  be  associated. 
.  It  is  the  work  of  a  master  of  the  subject,  who  is  not 
only  a  scientific  man  in  the  sense  of  being  an  observer,  but  also 
in  the  sense  of  having  a  true  philosophical  mind." — The  Lancet . 

"To  one  who  wishes  to  know  what  bacteriology  has  accom- 
plished and  what  problems  are  still  undergoing  solution,  no- 
thing can  serve  better  than  this  outline  of  Professor  Hueppe." 
— Science. 

"The  publishers  deserve  special  credit  for  the  acceptable 
form  in  which  this  work  is  presented;  and  the  clearness  of  the 
type,  as  well  as  of  illustrations,  place  this  volume  beyond  all 
criticism . ' ' — Medical  Fortnightly . 

GEORGE  JOHN  ROMANES 

Romanes  is  generally  characterized  as  the  man  upon  whom 
the  mantle  of  Darwin  has  fallen.  He  was  a  disciple 
and  an  intimate  personal  friend  of  the  great  expounder 
of  the  doctrine  of  evolution.  His  three-volume  work, 
Darwin  and  after  Darwin,  together  with  the  additional 
volume,  An  Examination  of  Weismannism  have  become 
classical. 

Darwin  and  After  Darwin,  An  Exposition  of  the  Dar- 
winian Theory  and  a  Discussion  of  Post-Darwinian 
Questions,  by  George  John  Romanes,  M.  A.,  LL.  D., 
F.  R.  S.,  Honorary  Fellow  of  Gonville  and  Caius 
College,  Cambridge.     Three  volumes.     $4.00  net. 

Part  I.  The  Darwinian  Theory.  Third  edition.  1901. 
Pp.  xiv.,  460.     Cloth  $2.00. 

Part  II.  Post  -  Darwinian  Questions :  Heredity  and  Utility. 
Second  edition.     1897.     Pp.  xii.,  344.     Cloth  $1.50. 


4  OPEN  COURT  BIOLOGICAL  SERIES. 

George  John  Romanes — Continued 

Part  III.  Post  -  Darwinian  Questions:  Isolation  and  Physio- 
logical Selection.     1897.      Pp.  181.    Cloth  $1.00. 

An  Examination  of  Weismannism,  by  George  John  Romanes, 
M.  A.,  LL.  D.,  F.  R.  S.,  Honorary  Fellow  of  Gonville 
and  Caius  College,  Cambridge.  Second  edition.  1899. 
Pp.  ix.,  221.     Cloth  $1.00  net. 

D.  KERFOOT  SHUTE,  M.  D. 

Dr.  Shute's  First  Book  in  Organic  Evolution  originated  in 
the  lecture  room,  its  author  being  the  professor  of 
Anatomy  in  the  medical  department  of  the  Columbian 
University  at  Washington.  Students  of  this  subject 
who  have  not  the  benefit  of  attending  a  university  can 
easily  post  themselves  with  the  help  of  this  little 
volume,  so  terse  and  so  clear  in  all  essentials. 

A  First  Book  in  Organic  Evolution,  an  Introduction  to  the 
Study  of  the  Development  Theory,  by  D.  Kerfoot 
Shute,  M.  D.  Pp.  xvi.,  285;  39  illustrations,  9  in 
natural  colors.     Price  cloth,  $2.00  net  (7s.  6d.  net). 

"It  is  difficult  to  see  in  what  way  this  volume  could  be  im- 
proved. The  elementary  part  of  the  doctrine  of  evolution  is 
thoroui^hly  covered  and  without  a  word  wasted,  and  the  arrange- 
ment of  the  matter  presented  is  scholarly.  It  is  just  such  a 
volume  as  teachers  everywhere  are  looking  for  to  give  those 
interested  a  first-class  idea  of  the  modern  biological  beliefs." 
— Americafi  Inventor. 

"It  seems  to  us  that  the  author  has  attained  no  small  success 
in  his  difficult  task,  for  the  book  is  clear  and  interesting;  it  is 
neither  too  simple  nor  too  difficult;  it  is  conspicuously  free  from 
crankiness  and  dogmatism,  and  it  is  evidently  the  work  of  one 
who  has  had  experience  in  the  task  of  teaching.  Prof.  Shute 
is  to  be  congratulated  on  the  success  with  which  he  has  accom- 
plished a  difficult  and  serviceable  piece  of  work." — Nature. 

AUGUST  WEISMANN 

On  Germinal  Selection,  as  a  vSource  of  Definite  Variation, 
by  August  Weismann.  Translated  from  the  German 
by  Thomas  J.  McCormack.  Second  edition.  1902. 
Pp.  87.     Cloth  60c  net  (3s  net). 

"Forms  the  crown  and  capsheaf  of  Weismann's  celebrated 
Theory  of  Heredity." 

In  connection  with  the  subject  of  this  book,  see  also  An  Examination  of 
Weismannism,  by  George  John  Romanes,  page  4,  and  On  Ortho- 
genesis; or,  The  Impotence  of  Darwinian  Selection  in  the  Formation  of 
Species,  by  Th.  Eimer,  page  2,  which  was  written  in  reply  to 
Weismann's  Germinal  Selection. 


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